fix(calls): "Channel Full" counts people, not devices (#342)

useVoiceChannelFull compared the number of MatrixRTC memberships (one per
device) with io.lotus.voice_limit, so one person on desktop + phone, or a
crashed tab whose membership hadn't expired, filled two slots and locked
others out, while the server-side guard (which counts distinct users)
would have admitted them. utils/voiceChannelFull.ts (unit-tested) counts
distinct senders; the header/sidebar counter shows people too.

Verified on the local stack: limit 2, @aud_main in the call on two
devices; @aud_bob's prescreen now shows 1/2 with Join enabled (was
"Channel Full (2/2)"), matching the guard's 200.

Fixes #342

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

src/app/hooks/useVoiceChannelFull.ts

@@ -5,6 +5,7 @@ import { StateEvent } from '../../types/matrix/room';
 import { VoiceLimitContent } from '../features/common-settings/general/RoomVoiceLimit';
 import { useCallMembers, useCallSession } from './useCall';
 import { useMatrixClient } from './useMatrixClient';
+import { voiceChannelOccupancy } from '../utils/voiceChannelFull';
 
 export type VoiceChannelFull = {
   channelFull: boolean;
@@ -26,9 +27,11 @@ export const useVoiceChannelFull = (room: Room): VoiceChannelFull => {
 
   return useMemo(() => {
     const maxUsers = limitEvent?.getContent<VoiceLimitContent>().max_users ?? 0;
-    // A user already counted in the session is rejoining and should not be blocked.
-    const alreadyMember = callMembers.some((m) => m.sender === mx.getSafeUserId());
-    const channelFull = maxUsers > 0 && !alreadyMember && callMembers.length >= maxUsers;
-    return { channelFull, current: callMembers.length, max: maxUsers };
+    // Distinct people, not per-device memberships (Gitea #342).
+    return voiceChannelOccupancy(
+      callMembers.map((m) => m.sender),
+      mx.getSafeUserId(),
+      maxUsers,
+    );
   }, [limitEvent, callMembers, mx]);
 };