feat(03-12): GREEN — WR-07 real focus trap on EventForm dialog

Add Tab/Shift+Tab focus trap to the dialog element:
- onKeyDown handler queries all focusable elements inside dialogRef
- Tab from last element wraps to first (preventDefault)
- Shift+Tab from first element wraps to last (preventDefault)
- No new dependency — implemented inline with dialogRef
- Existing focus-on-open (titleRef) and Escape-to-close unchanged
- Update docblock: focus trap claim is now accurate (WR-07)

apps/pwa/src/components/EventForm.tsx

@@ -21,6 +21,7 @@
  * Accessibility:
  *   - role="dialog", aria-modal="true", aria-label="New Event"/"Edit Event"
  *   - Focus moves to Title input on open
+ *   - Focus trap: Tab/Shift+Tab cycle focus within dialog; never reaches background (WR-07)
  *   - Escape / backdrop click closes form
  *   - All-day toggle: role="switch", aria-checked
  *   - Recurrence: <select> with labeled options
@@ -111,6 +112,7 @@ export function EventForm() {
   const setLastSyncedUid = useCalendarStore((s) => s.setLastSyncedUid)
   const queryClient = useQueryClient()
   const titleRef = useRef<HTMLInputElement>(null)
+  const dialogRef = useRef<HTMLDivElement>(null)
 
   // ── Resolve event for edit mode ─────────────────────────────────────────────
 
@@ -285,6 +287,42 @@ export function EventForm() {
     return () => document.removeEventListener('keydown', onKeyDown)
   }, [eventFormOpen]) // eslint-disable-line react-hooks/exhaustive-deps
 
+  // ── Focus trap: Tab / Shift+Tab cycles within dialog (WR-07) ───────────────
+  //
+  // Queries all standard focusable elements inside the dialog on each keydown.
+  // If Tab is pressed on the last focusable element, wraps to the first.
+  // If Shift+Tab is pressed on the first focusable element, wraps to the last.
+  // No external library — implemented inline to avoid adding a dependency.
+
+  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) {
+      // Shift+Tab: if on first element, wrap to last
+      if (document.activeElement === first) {
+        e.preventDefault()
+        last.focus()
+      }
+    } else {
+      // Tab: if on last element, wrap to first
+      if (document.activeElement === last) {
+        e.preventDefault()
+        first.focus()
+      }
+    }
+  }
+
   // ── Focus: move to title input on open ─────────────────────────────────────
 
   useEffect(() => {
@@ -392,10 +430,12 @@ export function EventForm() {
 
       {/* Dialog */}
       <div
+        ref={dialogRef}
         role="dialog"
         aria-modal="true"
         aria-label={label}
         tabIndex={-1}
+        onKeyDown={handleDialogKeyDown}
         style={dialogStyle}
       >
         {/* Header */}