feat(threads): Slack-style per-thread notifications (P4-1)

Default = Participating: thread replies notify only when you've posted in the
thread or are @mentioned; per-thread override to All / Mentions-only / Mute via
a bell menu in the thread panel header. Modes sync across devices in
io.lotus.thread_notifications account data (pruned on write: left rooms, >180d,
cap 200/room). Muted threads: no notifications/sounds, chip badge suppressed
(+BellMute glyph), and their counts are subtracted from the room's sidebar
badge (client-side; clamped ≥0).

Also fixes the thread notification path itself: thread replies are now owned by
exactly ONE handler (room-level ThreadEvent.NewReply via a new useRoomsListener
hook, with per-thread dedupe, panel-aware focus suppression, and per-thread OS
tag coalescing) — the existing RoomEvent.Timeline handlers in the notifier and
the unread binder are explicitly thread-guarded, eliminating the previously
un-gated/double path. Room badges now also refresh live on
RoomEvent.UnreadNotifications (surgical per-room PUT; fixes thread-badge lag).

Pure decision core shouldNotifyThreadReply (13-case matrix) + prune + unread
subtraction: +32 tests (648 total). E2EE caveat documented: mentions-only may
under-notify pre-decryption (same class as the existing path).

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

src/app/utils/room.ts

@@ -29,6 +29,7 @@ import {
   StateEvent,
   UnreadInfo,
 } from '../../types/matrix/room';
+import { getMutedThreads, ThreadNotificationsContent } from './threadNotifications';
 
 export const getStateEvent = (
   room: Room,
@@ -233,9 +234,23 @@ export const roomHaveUnread = (mx: MatrixClient, room: Room) => {
   return true;
 };
 
-export const getUnreadInfo = (room: Room): UnreadInfo => {
-  const total = room.getUnreadNotificationCount(NotificationCountType.Total);
-  const highlight = room.getUnreadNotificationCount(NotificationCountType.Highlight);
+export const getUnreadInfo = (room: Room, mutedThreads?: Set<string>): UnreadInfo => {
+  let total = room.getUnreadNotificationCount(NotificationCountType.Total);
+  let highlight = room.getUnreadNotificationCount(NotificationCountType.Highlight);
+
+  // Server room totals INCLUDE per-thread notification counts, so subtract any
+  // explicitly muted thread's counts back out (clamped at zero) to keep muted
+  // threads from contributing to the room badge (P4-1).
+  if (mutedThreads && mutedThreads.size > 0) {
+    mutedThreads.forEach((threadId) => {
+      total -= room.getThreadUnreadNotificationCount(threadId, NotificationCountType.Total) ?? 0;
+      highlight -=
+        room.getThreadUnreadNotificationCount(threadId, NotificationCountType.Highlight) ?? 0;
+    });
+    if (total < 0) total = 0;
+    if (highlight < 0) highlight = 0;
+  }
+
   return {
     roomId: room.roomId,
     highlight,
@@ -243,14 +258,18 @@ export const getUnreadInfo = (room: Room): UnreadInfo => {
   };
 };
 
-export const getUnreadInfos = (mx: MatrixClient): UnreadInfo[] => {
+export const getUnreadInfos = (
+  mx: MatrixClient,
+  content?: ThreadNotificationsContent,
+): UnreadInfo[] => {
   const unreadInfos = mx.getRooms().reduce<UnreadInfo[]>((unread, room) => {
     if (room.isSpaceRoom()) return unread;
     if (room.getMyMembership() !== 'join') return unread;
     if (getNotificationType(mx, room.roomId) === NotificationType.Mute) return unread;
 
     if (roomHaveNotification(room) || roomHaveUnread(mx, room)) {
-      unread.push(getUnreadInfo(room));
+      const mutedThreads = content ? getMutedThreads(content, room.roomId) : undefined;
+      unread.push(getUnreadInfo(room, mutedThreads));
     }
 
     return unread;