feat(06-06): add whole-series edit confirmation prompt

- Create SeriesEditPrompt.tsx: bottom-sheet (phone) / dialog (desktop) matching
  DeleteConfirmationDialog pattern; focus trap, Escape=cancel, role=dialog/aria-modal
- UI-SPEC Surface 6 copy: 'Edit recurring series' heading, 'This will update all
  occurrences of this event.' body, 'Update series' accent-filled CTA, 'Cancel' ghost
- Import SeriesEditPrompt + add seriesEditPromptOpen state to EventForm
- handleSubmit gates on occurrence.hasRrule: opens prompt for recurring edits;
  executeSubmit() fires the existing whole-series PATCH on confirmation
- Save CTA label becomes 'Update series' for recurring edits (UI-SPEC primary CTAs)
- Non-recurring and create-mode Save behavior unchanged (no prompt)

apps/pwa/src/components/EventForm.tsx

@@ -45,6 +45,7 @@ import {
   computeNewTimedEnd,
   computeNewAllDayEnd,
 } from '../lib/eventDateTime.js'
+import { SeriesEditPrompt } from './SeriesEditPrompt.js'
 
 // ── Constants ─────────────────────────────────────────────────────────────────
 
@@ -276,6 +277,8 @@ export function EventForm() {
   // ── Validation state ────────────────────────────────────────────────────────
 
   const [errors, setErrors] = useState<{ title?: string; endTime?: string; recurrenceBound?: string }>({})
+  // D-08/D-09: series-edit confirmation prompt state
+  const [seriesEditPromptOpen, setSeriesEditPromptOpen] = useState(false)
 
   // ── Mutations ───────────────────────────────────────────────────────────────
 
@@ -360,9 +363,13 @@ export function EventForm() {
     return Object.keys(newErrors).length === 0
   }
 
-  const handleSubmit = () => {
+  /**
-    if (!validate()) return
+   * Build the payload and fire the mutation. Called directly for non-recurring edits
-
+   * and create mode; called from the SeriesEditPrompt onConfirm for recurring edits
+   * (D-08/D-09). The whole-series PATCH reuses the existing /api/events/:uid/edit route
+   * which PUTs the master VEVENT — no RECURRENCE-ID, per D-08.
+   */
+  const executeSubmit = () => {
     // BUG A fix: serialize timed events to an unambiguous UTC instant here in
     // the browser (operator's zone is known) instead of sending a naive local
     // wall-clock string. The API container is UTC; a naive string was being read
@@ -403,6 +410,20 @@ export function EventForm() {
     mutation.mutate(payload)
   }
 
+  const handleSubmit = () => {
+    if (!validate()) return
+
+    const isEdit = eventFormMode === 'edit' && !!eventFormUid
+
+    // D-08/D-09: gate recurring-series edits behind the confirmation prompt
+    if (isEdit && occurrence?.hasRrule === true) {
+      setSeriesEditPromptOpen(true)
+      return
+    }
+
+    executeSubmit()
+  }
+
   // ── Keyboard: Escape to close ───────────────────────────────────────────────
 
   useEffect(() => {
@@ -466,11 +487,15 @@ export function EventForm() {
 
   const isPhone = isPhoneBreakpoint()
   const label = eventFormMode === 'edit' ? 'Edit Event' : 'New Event'
+  // D-08/D-09: CTA label is "Update series" for recurring edits (UI-SPEC "EventForm primary CTAs")
+  const isEditRecurring = eventFormMode === 'edit' && occurrence?.hasRrule === true
   const saveLabel = mutation.isPending
     ? 'Saving…'
-    : eventFormMode === 'edit'
+    : isEditRecurring
-      ? 'Save Changes'
+      ? 'Update series'
-      : 'Create Event'
+      : eventFormMode === 'edit'
+        ? 'Save Changes'
+        : 'Create Event'
 
   const dialogStyle: React.CSSProperties = isPhone
     ? {
@@ -1014,6 +1039,16 @@ export function EventForm() {
           </button>
         </div>
       </div>
+
+      {/* D-08/D-09: Series-edit confirmation prompt — shown when editing a recurring occurrence */}
+      <SeriesEditPrompt
+        open={seriesEditPromptOpen}
+        onConfirm={() => {
+          setSeriesEditPromptOpen(false)
+          executeSubmit()
+        }}
+        onCancel={() => setSeriesEditPromptOpen(false)}
+      />
     </>
   )
 }

apps/pwa/src/components/SeriesEditPrompt.tsx

@@ -0,0 +1,223 @@
+/**
+ * SeriesEditPrompt — whole-series edit confirmation sheet/dialog (Plan 06-06).
+ *
+ * D-08/D-09: Editing a recurring occurrence must confirm before submitting the
+ * whole-series PATCH (which PUTs the master VEVENT back to Fastmail without a
+ * RECURRENCE-ID, updating all occurrences). This prompt gates that submit.
+ *
+ * Trigger: EventForm calls setOpen(true) when in edit mode with occurrence.hasRrule===true.
+ * Confirm: "Update series" — runs the existing whole-series PATCH; no new privilege.
+ * Cancel: Escape or "Cancel" button — returns to the form without submitting.
+ *
+ * Layout (Surface 6 — UI-SPEC):
+ *   - Phone (≤767px): bottom sheet (full-screen overlay, slide from below)
+ *   - Tablet/desktop (≥768px): centered dialog (max-width 480px)
+ *
+ * Accessibility:
+ *   - role="dialog", aria-modal="true", aria-labelledby → heading
+ *   - Focus trap: Tab/Shift+Tab cycle between Cancel and Update series
+ *   - Escape key fires Cancel
+ *
+ * Security: T-03-15 — all text rendered as plain-text JSX children.
+ * NEVER use dangerouslySetInnerHTML here.
+ */
+
+import { useEffect, useRef } from 'react'
+
+// ── Component ─────────────────────────────────────────────────────────────────
+
+interface SeriesEditPromptProps {
+  open: boolean
+  onConfirm: () => void
+  onCancel: () => void
+}
+
+export function SeriesEditPrompt({ open, onConfirm, onCancel }: SeriesEditPromptProps) {
+  const dialogRef = useRef<HTMLDivElement>(null)
+  const headingId = 'series-edit-prompt-heading'
+
+  // Focus trap — focus the dialog when it opens
+  useEffect(() => {
+    if (open && dialogRef.current) {
+      dialogRef.current.focus()
+    }
+  }, [open])
+
+  // Escape key listener — cancel without submitting
+  useEffect(() => {
+    if (!open) return
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') {
+        onCancel()
+      }
+    }
+    document.addEventListener('keydown', onKeyDown)
+    return () => document.removeEventListener('keydown', onKeyDown)
+  }, [open, onCancel])
+
+  // Focus trap: Tab / Shift+Tab cycles within dialog
+  const handleDialogKeyDown = (e: React.KeyboardEvent<HTMLDivElement>) => {
+    if (e.key !== 'Tab' || !dialogRef.current) return
+
+    const focusable = Array.from(
+      dialogRef.current.querySelectorAll<HTMLElement>(
+        'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])',
+      ),
+    ).filter((el) => !el.hasAttribute('disabled') && el.getAttribute('tabindex') !== '-1')
+
+    if (focusable.length === 0) return
+
+    const first = focusable[0]
+    const last = focusable[focusable.length - 1]
+
+    if (e.shiftKey) {
+      if (document.activeElement === first) {
+        e.preventDefault()
+        last.focus()
+      }
+    } else {
+      if (document.activeElement === last) {
+        e.preventDefault()
+        first.focus()
+      }
+    }
+  }
+
+  if (!open) return null
+
+  const isPhone = typeof window !== 'undefined' && window.matchMedia('(max-width: 767px)').matches
+
+  const dialogStyle: React.CSSProperties = isPhone
+    ? {
+        position: 'fixed',
+        bottom: 0,
+        left: 0,
+        right: 0,
+        background: 'var(--color-surface-raised)',
+        borderRadius: 'var(--space-3) var(--space-3) 0 0',
+        boxShadow: '0 -4px 24px rgba(0,0,0,0.12)',
+        padding: 'var(--space-6)',
+        zIndex: 400,
+        fontFamily: 'var(--font-family-base)',
+      }
+    : {
+        position: 'fixed',
+        top: '50%',
+        left: '50%',
+        transform: 'translate(-50%, -50%)',
+        background: 'var(--color-surface-raised)',
+        borderRadius: 'var(--space-2)',
+        boxShadow: '0 8px 32px rgba(0,0,0,0.16)',
+        padding: 'var(--space-6)',
+        width: '100%',
+        maxWidth: '480px',
+        zIndex: 400,
+        fontFamily: 'var(--font-family-base)',
+      }
+
+  return (
+    <>
+      {/* Backdrop */}
+      <div
+        onClick={onCancel}
+        aria-hidden="true"
+        style={{
+          position: 'fixed',
+          inset: 0,
+          background: 'var(--color-overlay)',
+          zIndex: 399,
+        }}
+      />
+
+      {/* Dialog */}
+      <div
+        ref={dialogRef}
+        role="dialog"
+        aria-modal="true"
+        aria-labelledby={headingId}
+        tabIndex={-1}
+        onKeyDown={handleDialogKeyDown}
+        style={dialogStyle}
+      >
+        {/* Heading */}
+        <h2
+          id={headingId}
+          style={{
+            margin: '0 0 var(--space-3) 0',
+            fontSize: 'var(--text-heading-size)',
+            fontWeight: 'var(--text-heading-weight)',
+            lineHeight: 'var(--text-heading-line-height)',
+            color: 'var(--color-text-primary)',
+          }}
+        >
+          {/* Plain text — XSS guard (T-03-15) */}
+          Edit recurring series
+        </h2>
+
+        {/* Body */}
+        <p
+          style={{
+            margin: '0 0 var(--space-6) 0',
+            fontSize: 'var(--text-body-size)',
+            fontWeight: 'var(--text-body-weight)',
+            lineHeight: 'var(--text-body-line-height)',
+            color: 'var(--color-text-secondary)',
+          }}
+        >
+          {/* Plain text — XSS guard (T-03-15) */}
+          This will update all occurrences of this event.
+        </p>
+
+        {/* Actions */}
+        <div
+          style={{
+            display: 'flex',
+            justifyContent: 'flex-end',
+            gap: 'var(--space-3)',
+            alignItems: 'center',
+          }}
+        >
+          {/* Cancel — ghost style */}
+          <button
+            onClick={onCancel}
+            style={{
+              background: 'none',
+              border: 'none',
+              cursor: 'pointer',
+              minHeight: '44px',
+              padding: '0 var(--space-4)',
+              borderRadius: 'var(--space-1)',
+              fontSize: 'var(--text-label-size)',
+              fontWeight: 600,
+              color: 'var(--color-text-secondary)',
+              fontFamily: 'var(--font-family-base)',
+            }}
+          >
+            {/* Plain text — XSS guard (T-03-15) */}
+            Cancel
+          </button>
+
+          {/* Update series — accent-filled (NOT destructive — this is an edit) */}
+          <button
+            onClick={onConfirm}
+            style={{
+              background: 'var(--color-member-0)',
+              border: 'none',
+              cursor: 'pointer',
+              minHeight: '44px',
+              padding: '0 var(--space-4)',
+              borderRadius: 'var(--space-1)',
+              fontSize: 'var(--text-label-size)',
+              fontWeight: 600,
+              color: '#ffffff',
+              fontFamily: 'var(--font-family-base)',
+            }}
+          >
+            {/* Plain text — XSS guard (T-03-15) */}
+            Update series
+          </button>
+        </div>
+      </div>
+    </>
+  )
+}