feat: personal room name overrides (MSC4431-style)

Users can right-click any room and 'Rename for me...' to set a local
display name visible only to them. Stored in account data under
io.lotus.room_names. Shows a pencil indicator on renamed rooms.
useLocalRoomName() hook overrides useRoomName() when a local name exists.

Also includes:
- Rich room topic rendering via RoomTopicContent object (formatted_body
  support in RoomTopicViewer with HTML sanitization via sanitizeCustomHtml)
- Edit history viewer: clicking '(edited)' on a message opens a modal
  showing all prior versions with timestamps (EditHistoryModal.tsx)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/RoomTimeline.tsx

@@ -128,6 +128,7 @@ import { useAccessiblePowerTagColors, useGetMemberPowerTag } from '../../hooks/u
 import { useTheme } from '../../hooks/useTheme';
 import { useRoomCreatorsTag } from '../../hooks/useRoomCreatorsTag';
 import { usePowerLevelTags } from '../../hooks/usePowerLevelTags';
+import { EditHistoryModal } from './message/EditHistoryModal';
 
 const TimelineFloat = as<'div', css.TimelineFloatVariants>(
   ({ position, className, ...props }, ref) => (
@@ -480,6 +481,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
   const canSendReaction = permissions.event(MessageEvent.Reaction, mx.getSafeUserId());
   const canPinEvent = permissions.stateEvent(StateEvent.RoomPinnedEvents, mx.getSafeUserId());
   const [editId, setEditId] = useState<string>();
+  const [editHistoryEvent, setEditHistoryEvent] = useState<MatrixEvent | undefined>();
 
   const roomToParents = useAtomValue(roomToParentsAtom);
   const unread = useRoomUnread(room.roomId, roomToUnreadAtom);
@@ -1123,6 +1125,9 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
                 msgType={mEvent.getContent().msgtype ?? ''}
                 ts={mEvent.getTs()}
                 edited={!!editedEvent}
+                onEditHistoryClick={
+                  editedEvent ? () => setEditHistoryEvent(mEvent) : undefined
+                }
                 getContent={getContent}
                 mediaAutoLoad={mediaAutoLoad}
                 urlPreview={showUrlPreview}
@@ -1229,6 +1234,9 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
                       msgType={mEvent.getContent().msgtype ?? ''}
                       ts={mEvent.getTs()}
                       edited={!!editedEvent}
+                      onEditHistoryClick={
+                        editedEvent ? () => setEditHistoryEvent(mEvent) : undefined
+                      }
                       getContent={getContent}
                       mediaAutoLoad={mediaAutoLoad}
                       urlPreview={showUrlPreview}
@@ -2191,6 +2199,13 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
           </TimelineFloat>
         )}
       </Box>
+      {editHistoryEvent && (
+        <EditHistoryModal
+          room={room}
+          mEvent={editHistoryEvent}
+          onClose={() => setEditHistoryEvent(undefined)}
+        />
+      )}
     </ReadPositionsContext.Provider>
   );
 }