fix(a11y): review-wave fixes (P3-4)

- `?` shortcut now stopImmediatePropagation so RoomView's type-to-focus handler
  doesn't steal focus into the composer behind the dialog (and swallow Escape) —
  CONFIRMED review finding.
- Typing live region stays mounted (empty when idle) so the FIRST "X is typing"
  is reliably announced (a status region added with its text isn't always read).
- Removed a stray empty `{}` JSX expression in MediaGallery (leftover from an
  auto-fix).

Reviewer verified the rest: collapsed-message labels, focus-return
classification (4 dialogs fixed, popouts correctly left), and all aria fixes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/MediaGallery.tsx

@@ -261,7 +261,6 @@ function Lightbox({
           escapeDeactivates: false,
         }}
       >
-        {}
         <div
           role="dialog"
           aria-modal

src/app/features/room/RoomViewTyping.tsx

@@ -33,11 +33,10 @@ export const RoomViewTyping = as<'div', RoomViewTypingProps>(
       [typingMembers, myUserId, room],
     );
 
-    if (typingNames.length === 0) {
-      return null;
-    }
-
     // A single, non-truncated string for assistive technology to announce.
+    // Computed even when empty so the live region can stay mounted (below) —
+    // a `role="status"` region added to the DOM together with its first text
+    // is not reliably announced by some screen readers.
     let typingAnnouncement = '';
     if (typingNames.length === 1) {
       typingAnnouncement = `${typingNames[0]} is typing`;
@@ -65,9 +64,11 @@ export const RoomViewTyping = as<'div', RoomViewTypingProps>(
 
     return (
       <div style={{ position: 'relative' }}>
+        {/* Persistently mounted so the FIRST "X is typing" is announced. */}
         <span className={css.SrOnly} role="status" aria-live="polite" aria-atomic="true">
           {typingAnnouncement}
         </span>
+        {typingNames.length > 0 && (
           <Box
             className={classNames(css.RoomViewTyping, className)}
             alignItems="Center"
@@ -144,6 +145,7 @@ export const RoomViewTyping = as<'div', RoomViewTypingProps>(
               <Icon size="50" src={Icons.Cross} />
             </IconButton>
           </Box>
+        )}
       </div>
     );
   },

src/app/features/shortcuts/KeyboardShortcutsDialog.tsx

@@ -55,6 +55,10 @@ export function useKeyboardShortcutsTrigger() {
         // `?` is produced by Shift + `/` on the common layouts.
         if (evt.key === '?') {
           evt.preventDefault();
+          // Stop RoomView's window-level "type any char → focus composer"
+          // handler from also firing — otherwise focus lands in the composer
+          // behind the dialog and Escape gets swallowed by the contenteditable.
+          evt.stopImmediatePropagation();
           setOpen(true);
         }
       },