fix(calls): sidebar voice-channel join respects the voice limit

channelFull was computed only in the prescreen; a second click on the
channel in the room nav joined a full channel. Extract
useVoiceChannelFull, use it in both places, and refuse with a
"Channel full (N/N)" toast.

Fixes #30

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

src/app/features/room-nav/RoomNavItem.tsx

@@ -80,6 +80,7 @@ import {
 } from '../../hooks/useRoomMeta';
 import { useCallMembers, useCallSession } from '../../hooks/useCall';
 import { useCallEmbed, useCallStart } from '../../hooks/useCallEmbed';
+import { useVoiceChannelFull } from '../../hooks/useVoiceChannelFull';
 import { callChatAtom } from '../../state/callEmbed';
 import { createErrorToast, toastQueueAtom } from '../../state/toast';
 import { useCallPreferencesAtom } from '../../state/hooks/callPreferences';
@@ -691,8 +692,12 @@ function RoomNavItem_({
   const callMembers = useCallMembers(callSession);
   const startCall = useCallStart(direct);
   const callEmbed = useCallEmbed();
+  // [Gitea #30] Same voice-limit check the call prescreen uses, so the sidebar
+  // second-click join path can't bypass a full channel.
+  const { channelFull, current: voiceCurrent, max: voiceMax } = useVoiceChannelFull(room);
   const callPref = useAtomValue(useCallPreferencesAtom());
   const autoDiscoveryInfo = useAutoDiscoveryInfo();
+  const setToast = useSetAtom(toastQueueAtom);
 
   const handleStartCall: MouseEventHandler<HTMLAnchorElement> = (evt) => {
     const powerLevelsEvent = getStateEvent(room, StateEvent.RoomPowerLevels);
@@ -714,6 +719,22 @@ function RoomNavItem_({
     if (callEmbed) {
       return;
     }
+
+    // [Gitea #30] Refuse to start a call into a full voice channel — the
+    // prescreen already blocks this, but the sidebar second-click join path
+    // skipped the check entirely.
+    if (channelFull) {
+      evt.preventDefault();
+      setToast(
+        createErrorToast(
+          `Channel full (${voiceCurrent}/${voiceMax})`,
+          Icons.Warning,
+          'Cannot join',
+        ),
+      );
+      return;
+    }
+
     // Start call in second click
     if (selected) {
       evt.preventDefault();