feat(03-07): InstallPrompt — iOS walkthrough banner + Android beforeinstallprompt

- Implement isIOSSafariNonStandalone(): iOS UA + navigator.standalone detection
- Implement useAndroidInstallPrompt(): captures beforeinstallprompt, exposes canInstall/triggerInstall
- InstallPrompt renders nothing when display-mode:standalone or navigator.standalone (already installed)
- iOS branch: dismissible banner with 'Install FamilySync' heading, 'How to install' link
  opens 5-step walkthrough sheet (exact UI-SPEC copy, orange #F5A623 step number annotation)
- Android branch: banner with 'Install' button shown only when canInstall=true
- localStorage.installPromptDismissed persists banner dismissal
- role="banner", dismiss aria-label="Dismiss install prompt", 44px touch targets
- Mount <InstallPrompt /> in CalendarShell (phone: below AppNav; desktop: top of content area)
- InstallPrompt.test.tsx GREEN (5 behavior tests); full PWA suite 44 tests green; tsc clean

apps/pwa/src/components/CalendarShell.tsx

@@ -48,6 +48,7 @@ import { EventDetailPopover } from './EventDetailPopover.js'
 import { AppNav } from './AppNav.js'
 import { ColorLegend } from './ColorLegend.js'
 import { SkeletonCalendar } from './SkeletonCalendar.js'
+import { InstallPrompt } from './InstallPrompt.js'
 
 // ── Helpers ────────────────────────────────────────────────────────────────
 
@@ -314,6 +315,7 @@ export function CalendarShell() {
           currentUserColor={meQuery.data?.user.color}
           currentUserName={meQuery.data?.user.displayName ?? undefined}
         />
+        <InstallPrompt />
         <CalendarContent />
         <EventDetailPopover />
       </div>
@@ -341,7 +343,10 @@ export function CalendarShell() {
       />
 
       {/* Main content area */}
+      <div style={{ flex: 1, minWidth: 0, display: 'flex', flexDirection: 'column', overflow: 'hidden' }}>
+        <InstallPrompt />
         <CalendarContent />
+      </div>
 
       {/* EventDetailPopover — standalone mode driven by Zustand openEventId */}
       <EventDetailPopover />

apps/pwa/src/components/InstallPrompt.tsx

@@ -0,0 +1,476 @@
+/**
+ * InstallPrompt — PWA install guidance for iOS and Android (PWA-01, PWA-02).
+ *
+ * Behaviors:
+ *   - Renders nothing when the app is already installed (display-mode: standalone
+ *     or navigator.standalone — iOS PWA).
+ *   - iOS Safari non-standalone: shows a dismissible banner with a "How to install"
+ *     link that opens a full-screen 5-step walkthrough sheet.
+ *   - Android (Chrome/Edge): shows a banner with an "Install" button only when the
+ *     `beforeinstallprompt` event has fired and canInstall is true.
+ *   - Neither surface shows when the app is already installed.
+ *
+ * localStorage key: `installPromptDismissed` — persists banner dismissal.
+ *
+ * Security: T-02d-01 — all text is plain-text JSX children; no dangerouslySetInnerHTML.
+ * Accessibility: role="banner", dismiss aria-label="Dismiss install prompt", 44px touch targets.
+ *
+ * CLAUDE.md PWA constraints:
+ *   - iOS 16.4+ minimum; Home-Screen install required for push.
+ *   - pushManager.subscribe() must be in a tap handler (enforced in Phase 5).
+ *   - EU DMA iOS 17.4+ caveat: PWA may open in Safari tabs; install guide addresses this.
+ */
+
+import { useState, useEffect } from 'react'
+import { Smartphone, X } from 'lucide-react'
+
+// ── iOS detection ──────────────────────────────────────────────────────────
+
+/**
+ * Returns true when the browser is iOS Safari in non-standalone (browser-tab) mode.
+ * Returns false when already installed (navigator.standalone === true) or on non-iOS.
+ *
+ * Detection logic:
+ *   1. Check for iPad/iPhone/iPod in UA (standard iOS Safari UA; excludes Android Chrome
+ *      which also contains "Safari").
+ *   2. Exclude IE/Edge for IE (MSStream property) — belt-and-suspenders.
+ *   3. Check navigator.standalone is NOT true (standalone = already installed).
+ */
+export function isIOSSafariNonStandalone(): boolean {
+  const ua = navigator.userAgent
+  const isIOS =
+    /iPad|iPhone|iPod/.test(ua) &&
+    !(window as unknown as { MSStream?: unknown }).MSStream
+  const isStandalone = (navigator as unknown as { standalone?: boolean }).standalone === true
+  return isIOS && !isStandalone
+}
+
+// ── Installed state check ──────────────────────────────────────────────────
+
+/**
+ * Returns true when the app is running in standalone mode (already installed).
+ * Covers both Android (display-mode media query) and iOS (navigator.standalone).
+ */
+function isInstalled(): boolean {
+  return (
+    window.matchMedia('(display-mode: standalone)').matches ||
+    (navigator as unknown as { standalone?: boolean }).standalone === true
+  )
+}
+
+// ── Android beforeinstallprompt hook ─────────────────────────────────────
+
+interface BeforeInstallPromptEvent extends Event {
+  prompt(): Promise<void>
+  userChoice: Promise<{ outcome: 'accepted' | 'dismissed' }>
+}
+
+/**
+ * Captures the browser's `beforeinstallprompt` event and exposes it as a hook.
+ * Only fires on Chrome/Edge on Android — never on iOS.
+ *
+ * Returns:
+ *   canInstall: true when the event has been captured and install is available
+ *   triggerInstall: function that calls prompt() on the deferred event
+ */
+export function useAndroidInstallPrompt() {
+  const [deferredPrompt, setDeferredPrompt] = useState<BeforeInstallPromptEvent | null>(null)
+
+  useEffect(() => {
+    const handler = (e: Event) => {
+      e.preventDefault()
+      setDeferredPrompt(e as BeforeInstallPromptEvent)
+    }
+    const installedHandler = () => setDeferredPrompt(null)
+
+    window.addEventListener('beforeinstallprompt', handler)
+    window.addEventListener('appinstalled', installedHandler)
+
+    return () => {
+      window.removeEventListener('beforeinstallprompt', handler)
+      window.removeEventListener('appinstalled', installedHandler)
+    }
+  }, [])
+
+  const triggerInstall = async () => {
+    if (!deferredPrompt) return
+    await deferredPrompt.prompt()
+    const { outcome } = await deferredPrompt.userChoice
+    if (outcome === 'accepted') {
+      setDeferredPrompt(null)
+    }
+  }
+
+  return { canInstall: deferredPrompt !== null, triggerInstall }
+}
+
+// ── iOS Walkthrough Sheet ─────────────────────────────────────────────────
+
+const IOS_STEPS = [
+  'Open FamilySync in Safari',
+  'Tap the Share button',
+  "Scroll down and tap 'Add to Home Screen'",
+  "Tap 'Add' in the top right",
+  'Open FamilySync from your Home Screen — it opens without the browser bar',
+]
+
+interface WalkthroughSheetProps {
+  onClose: () => void
+}
+
+function WalkthroughSheet({ onClose }: WalkthroughSheetProps) {
+  return (
+    <div
+      role="dialog"
+      aria-modal="true"
+      aria-label="Add to Home Screen walkthrough"
+      style={{
+        position: 'fixed',
+        inset: 0,
+        background: 'var(--color-overlay, rgba(0,0,0,0.5))',
+        display: 'flex',
+        flexDirection: 'column',
+        justifyContent: 'flex-end',
+        zIndex: 1000,
+      }}
+      onClick={(e) => {
+        // Close on backdrop click
+        if (e.target === e.currentTarget) onClose()
+      }}
+    >
+      <div
+        style={{
+          background: 'var(--color-surface, #ffffff)',
+          borderRadius: '12px 12px 0 0',
+          padding: 'var(--space-6, 24px)',
+          maxHeight: '90dvh',
+          overflowY: 'auto',
+          display: 'flex',
+          flexDirection: 'column',
+          gap: 'var(--space-4, 16px)',
+        }}
+      >
+        {/* Header */}
+        <div
+          style={{
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'space-between',
+          }}
+        >
+          <h2
+            style={{
+              margin: 0,
+              fontSize: 'var(--text-heading-size, 18px)',
+              fontWeight: 'var(--text-heading-weight, 600)',
+              lineHeight: 'var(--text-heading-line-height, 1.25)',
+              color: 'var(--color-text-primary, #111318)',
+              fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+            }}
+          >
+            Add to Home Screen
+          </h2>
+          <button
+            onClick={onClose}
+            aria-label="Close walkthrough"
+            style={{
+              background: 'none',
+              border: 'none',
+              cursor: 'pointer',
+              minWidth: '44px',
+              minHeight: '44px',
+              display: 'flex',
+              alignItems: 'center',
+              justifyContent: 'center',
+              color: 'var(--color-text-secondary, #5c6472)',
+              borderRadius: 'var(--space-1, 4px)',
+            }}
+          >
+            <X size={20} aria-hidden="true" />
+          </button>
+        </div>
+
+        {/* Steps */}
+        <ol
+          style={{
+            margin: 0,
+            padding: 0,
+            listStyle: 'none',
+            display: 'flex',
+            flexDirection: 'column',
+            gap: 'var(--space-4, 16px)',
+          }}
+        >
+          {IOS_STEPS.map((step, i) => (
+            <li
+              key={i}
+              style={{
+                display: 'flex',
+                alignItems: 'flex-start',
+                gap: 'var(--space-3, 12px)',
+              }}
+            >
+              {/* Step number with accent color annotation (#F5A623 — --color-member-2) */}
+              <span
+                style={{
+                  flexShrink: 0,
+                  width: '28px',
+                  height: '28px',
+                  borderRadius: '50%',
+                  background: '#F5A623',
+                  color: '#ffffff',
+                  display: 'flex',
+                  alignItems: 'center',
+                  justifyContent: 'center',
+                  fontSize: '13px',
+                  fontWeight: 600,
+                  fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+                }}
+              >
+                {i + 1}
+              </span>
+              <span
+                style={{
+                  fontSize: 'var(--text-body-size, 15px)',
+                  lineHeight: 'var(--text-body-line-height, 1.5)',
+                  color: 'var(--color-text-primary, #111318)',
+                  fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+                  paddingTop: '4px',
+                }}
+              >
+                {step}
+              </span>
+            </li>
+          ))}
+        </ol>
+
+        {/* Done button */}
+        <button
+          onClick={onClose}
+          style={{
+            background: 'var(--color-text-primary, #111318)',
+            color: '#ffffff',
+            border: 'none',
+            borderRadius: 'var(--space-1, 4px)',
+            minHeight: '44px',
+            padding: '0 var(--space-4, 16px)',
+            fontSize: 'var(--text-label-size, 13px)',
+            fontWeight: 600,
+            cursor: 'pointer',
+            fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+            alignSelf: 'stretch',
+          }}
+        >
+          Done
+        </button>
+      </div>
+    </div>
+  )
+}
+
+// ── InstallPrompt ─────────────────────────────────────────────────────────
+
+/**
+ * InstallPrompt renders the appropriate install surface based on platform:
+ *   - iOS Safari non-standalone: dismissible banner + optional walkthrough sheet
+ *   - Android (beforeinstallprompt available): install banner with native prompt button
+ *   - Already installed / desktop: nothing
+ *
+ * Mount this at the top level of CalendarShell, below the nav bar.
+ */
+export function InstallPrompt() {
+  const [dismissed, setDismissed] = useState<boolean>(
+    () => localStorage.getItem('installPromptDismissed') === '1',
+  )
+  const [walkthroughOpen, setWalkthroughOpen] = useState(false)
+  const { canInstall, triggerInstall } = useAndroidInstallPrompt()
+
+  // Re-check isInstalled on mount — matchMedia is only available in the browser
+  const [installed, setInstalled] = useState(false)
+  useEffect(() => {
+    setInstalled(isInstalled())
+  }, [])
+
+  // Nothing to show when already installed
+  if (installed) return null
+
+  function dismiss() {
+    localStorage.setItem('installPromptDismissed', '1')
+    setDismissed(true)
+  }
+
+  // ── iOS banner ──────────────────────────────────────────────────────────
+
+  if (isIOSSafariNonStandalone() && !dismissed) {
+    return (
+      <>
+        <div
+          role="banner"
+          style={{
+            display: 'flex',
+            alignItems: 'center',
+            gap: 'var(--space-3, 12px)',
+            padding: 'var(--space-3, 12px) var(--space-4, 16px)',
+            background: 'var(--color-surface-raised, #ffffff)',
+            borderBottom: '1px solid var(--color-border, #e2e4e9)',
+            fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+          }}
+        >
+          {/* Icon */}
+          <Smartphone
+            size={24}
+            aria-hidden="true"
+            style={{ color: 'var(--color-text-secondary, #5c6472)', flexShrink: 0 }}
+          />
+
+          {/* Text content */}
+          <div style={{ flex: 1, minWidth: 0 }}>
+            <div
+              style={{
+                fontSize: '13px',
+                fontWeight: 600,
+                color: 'var(--color-text-primary, #111318)',
+                lineHeight: 1.4,
+              }}
+            >
+              Install FamilySync
+            </div>
+            <div
+              style={{
+                fontSize: '13px',
+                color: 'var(--color-text-secondary, #5c6472)',
+                lineHeight: 1.4,
+              }}
+            >
+              Add to your Home Screen for the best experience.{' '}
+              <button
+                onClick={() => setWalkthroughOpen(true)}
+                style={{
+                  background: 'none',
+                  border: 'none',
+                  padding: 0,
+                  cursor: 'pointer',
+                  fontSize: '13px',
+                  color: 'var(--color-focus-ring, #4A90D9)',
+                  textDecoration: 'underline',
+                  fontFamily: 'inherit',
+                }}
+              >
+                How to install
+              </button>
+            </div>
+          </div>
+
+          {/* Dismiss */}
+          <button
+            onClick={dismiss}
+            aria-label="Dismiss install prompt"
+            style={{
+              background: 'none',
+              border: 'none',
+              cursor: 'pointer',
+              minWidth: '44px',
+              minHeight: '44px',
+              display: 'flex',
+              alignItems: 'center',
+              justifyContent: 'center',
+              color: 'var(--color-text-secondary, #5c6472)',
+              flexShrink: 0,
+              borderRadius: 'var(--space-1, 4px)',
+            }}
+          >
+            <X size={16} aria-hidden="true" />
+          </button>
+        </div>
+
+        {walkthroughOpen && <WalkthroughSheet onClose={() => setWalkthroughOpen(false)} />}
+      </>
+    )
+  }
+
+  // ── Android banner ──────────────────────────────────────────────────────
+
+  if (canInstall && !dismissed) {
+    return (
+      <div
+        role="banner"
+        style={{
+          display: 'flex',
+          alignItems: 'center',
+          gap: 'var(--space-3, 12px)',
+          padding: 'var(--space-3, 12px) var(--space-4, 16px)',
+          background: 'var(--color-surface-raised, #ffffff)',
+          borderBottom: '1px solid var(--color-border, #e2e4e9)',
+          fontFamily: 'var(--font-family-base, system-ui, sans-serif)',
+        }}
+      >
+        {/* Icon */}
+        <Smartphone
+          size={24}
+          aria-hidden="true"
+          style={{ color: 'var(--color-text-secondary, #5c6472)', flexShrink: 0 }}
+        />
+
+        {/* Text content */}
+        <div style={{ flex: 1, minWidth: 0 }}>
+          <div
+            style={{
+              fontSize: '13px',
+              color: 'var(--color-text-secondary, #5c6472)',
+              lineHeight: 1.4,
+            }}
+          >
+            Install FamilySync to your Home Screen for the best experience.
+          </div>
+        </div>
+
+        {/* Install CTA */}
+        <button
+          onClick={() => {
+            void triggerInstall().then(() => dismiss())
+          }}
+          style={{
+            background: 'var(--color-text-primary, #111318)',
+            color: '#ffffff',
+            border: 'none',
+            borderRadius: 'var(--space-1, 4px)',
+            minHeight: '44px',
+            padding: '0 var(--space-4, 16px)',
+            fontSize: '13px',
+            fontWeight: 600,
+            cursor: 'pointer',
+            fontFamily: 'inherit',
+            flexShrink: 0,
+            whiteSpace: 'nowrap',
+          }}
+        >
+          Install
+        </button>
+
+        {/* Dismiss */}
+        <button
+          onClick={dismiss}
+          aria-label="Dismiss install prompt"
+          style={{
+            background: 'none',
+            border: 'none',
+            cursor: 'pointer',
+            minWidth: '44px',
+            minHeight: '44px',
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'center',
+            color: 'var(--color-text-secondary, #5c6472)',
+            flexShrink: 0,
+            borderRadius: 'var(--space-1, 4px)',
+          }}
+        >
+          <X size={16} aria-hidden="true" />
+        </button>
+      </div>
+    )
+  }
+
+  // Nothing applicable — desktop, already installed, or dismissed
+  return null
+}