feat(calls): live-call dot on the space rail (#148)

A small red dot on a space tab when any room in that space (recursively)
has an active MatrixRTC session, so a live call is visible even when you
are looking at a different space or your DMs. Hidden while the space is
selected — the room list already shows the Live badge there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/hooks/useSpaceLiveCall.ts

@@ -0,0 +1,46 @@
+import { useEffect, useMemo, useState } from 'react';
+import { MatrixEvent, RoomStateEvent } from 'matrix-js-sdk';
+import { MatrixRTCSessionManagerEvents } from 'matrix-js-sdk/lib/matrixrtc/MatrixRTCSessionManager';
+import { useMatrixClient } from './useMatrixClient';
+import { StateEvent } from '../../types/matrix/room';
+
+/**
+ * [Gitea #148] Whether any of the given rooms has a live MatrixRTC call.
+ * Derived from the same session memberships the sidebar voice rows use;
+ * recomputed only when a session starts/ends or a call-member state event
+ * lands in one of the rooms — no per-render scans.
+ */
+export function useAnyRoomLiveCall(roomIds: string[]): boolean {
+  const mx = useMatrixClient();
+  const idSet = useMemo(() => new Set(roomIds), [roomIds]);
+  const compute = () =>
+    roomIds.some((id) => {
+      const room = mx.getRoom(id);
+      return !!room && mx.matrixRTC.getRoomSession(room).memberships.length > 0;
+    });
+  const [live, setLive] = useState(compute);
+
+  useEffect(() => {
+    setLive(compute());
+    const onSession = (roomId: string) => {
+      if (idSet.has(roomId)) setLive(compute());
+    };
+    const onState = (event: MatrixEvent) => {
+      if (event.getType() !== StateEvent.GroupCallMemberPrefix) return;
+      const roomId = event.getRoomId();
+      if (roomId && idSet.has(roomId)) setLive(compute());
+    };
+    mx.matrixRTC.on(MatrixRTCSessionManagerEvents.SessionStarted, onSession);
+    mx.matrixRTC.on(MatrixRTCSessionManagerEvents.SessionEnded, onSession);
+    mx.on(RoomStateEvent.Events, onState);
+    return () => {
+      mx.matrixRTC.off(MatrixRTCSessionManagerEvents.SessionStarted, onSession);
+      mx.matrixRTC.off(MatrixRTCSessionManagerEvents.SessionEnded, onSession);
+      mx.off(RoomStateEvent.Events, onState);
+    };
+    // compute closes over roomIds; idSet changes exactly when roomIds does
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [mx, idSet]);
+
+  return live;
+}