fix(timeline): media gallery / activity log no longer make the timeline drop messages (#259)

The media gallery and activity log register filtered timeline sets on the
room (getOrCreateFilteredTimelineSet); the room re-emits their events as
live RoomEvent.Timeline, so every matching event reached "new event in
the room" listeners twice for the rest of the session. The timeline
window shifted by an extra message per event (loaded messages vanished),
and notifications, unread counts, widget feeds and ring handling saw
duplicates.

isFromFilteredTimelineSet() (unit-tested) identifies emits from a filtered
set; the room timeline, roomToUnread, message notifications, clock-skew
sampling, call ring/decline handling and widget event feeds ignore them.

Verified headless (40 messages, every 5th a file; gallery opened; Bob
sends 3 files + 1 text): before, the first rendered message drifted from
the room start to "file15"; now it stays put.

Fixes #259

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/room/RoomTimeline.tsx

@@ -90,6 +90,7 @@ import {
   isMembershipChanged,
   reactionOrEditEvent,
   sendRoomEvent,
+  isFromFilteredTimelineSet,
 } from '../../utils/room';
 import { getLastEditDiff } from '../../utils/editDiff';
 import { tick } from '../../utils/haptics';
@@ -410,6 +411,9 @@ const useLiveEventArrive = (room: Room, onArrive: (mEvent: MatrixEvent) => void)
       data,
     ) => {
       if (eventRoom?.roomId !== room.roomId || !data.liveEvent) return;
+      // [Gitea #259] The media gallery / activity log register filtered timeline
+      // sets whose events the room re-emits as live: don't count them twice.
+      if (isFromFilteredTimelineSet(data)) return;
       onArrive(mEvent);
     };
     const handleRedaction: RoomEventHandlerMap[RoomEvent.Redaction] = (mEvent, eventRoom) => {

src/app/features/room/widgets/RoomWidgetView.tsx

@@ -14,6 +14,7 @@ import { GeneralWidgetDriver } from './GeneralWidgetDriver';
 import { WidgetPermissionRequest, isWidgetUrlSafe } from './widgetUtils';
 import { restrictWidgetMessages } from '../../../plugins/widgetTransport';
 import { WidgetPermissionPrompt } from './WidgetPermissionPrompt';
+import { isFromFilteredTimelineSet } from '../../../utils/room';
 
 type PendingAsk = {
   requests: WidgetPermissionRequest[];
@@ -111,6 +112,7 @@ export function RoomWidgetView({ room, widget }: RoomWidgetViewProps) {
     };
     const onTimeline: RoomEventHandlerMap[RoomEvent.Timeline] = (ev, r, toStart, removed, data) => {
       if (toStart || removed || !data?.liveEvent) return;
+      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259] don't feed widgets each event twice
       if (ev.isBeingDecrypted()) ev.once(MatrixEventEvent.Decrypted, feed);
       else feed(ev);
     };