fix: low-tail correctness — thread notifs, call audio, OIDC expiry

Verify-then-fix batch of minor bugs; each staged diff reviewed by 2 agents
(both SHIP). Two listed items (N6 receipt-avatar refresh, H10 room-name
length reject) were already handled and left unchanged.

Threads:
- T5: a just-sent reply no longer under-notifies — `participated` also checks
  the local thread timeline for our own events, since the server-bundle
  `hasCurrentUserParticipated` lags.
- T6: a room set to "Mentions & Keywords only" no longer over-notifies Default
  thread replies — new `roomMentionsOnly` gate (behavior-identical when false;
  +4 unit tests).
- T7: thread-mode account-data writes are serialized with content carried
  forward (setAccountData is a bare PUT whose result lags the /sync echo, so
  plain serialization wouldn't stop the lost update); carry only on success.

Calls / audio:
- C-L2: a real incoming ring cancels a lingering Settings ringtone preview.
- C-L3: the ringtone AudioContext is primed on the first page gesture (via the
  always-mounted CallEmbedProvider) so the first ring after a cold load isn't
  silent.
- C-L5: useCallSpeakers depends on a stable boolean, so the tile MutationObserver
  + io.lotus.call_state subscription aren't rebuilt on every membership change.

Crypto:
- F5: the OIDC refresher forwards the freshly-refreshed token expiry
  (passed on the tokens object at runtime) as expiresInMs, so the persisted
  expiresAt no longer goes stale across reloads.

Gates: tsc 0, eslint 0, prettier clean, 860/860 tests, build ok.

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

src/app/hooks/useCallSpeakers.ts

@@ -25,8 +25,14 @@ export const useCallSpeakers = (callEmbed: CallEmbed): Set<string> => {
   const callMembers = useCallMembers(callSession);
   const joined = useCallJoined(callEmbed);
 
+  // C-L5 — depend on a STABLE boolean, not the callMembers array (whose identity
+  // changes on every membership change). The MutationObserver + io.lotus.call_state
+  // subscription below already track tiles joining/leaving live, so rebuilding
+  // them on each membership change is pure churn.
+  const hasCallMembers = callMembers.length > 0;
+
   useEffect(() => {
-    if (!callMembers || !joined) {
+    if (!hasCallMembers || !joined) {
       setSpeakers(new Set<string>());
       return undefined;
     }
@@ -126,7 +132,7 @@ export const useCallSpeakers = (callEmbed: CallEmbed): Set<string> => {
       bodyWatcher?.disconnect();
       unsubLotus();
     };
-  }, [callEmbed, callMembers, joined]);
+  }, [callEmbed, hasCallMembers, joined]);
 
   return speakers;
 };