feat(calls): room header chip for voice limit / audio-only policy (#134)

One small Surface chip next to the header controls, only when a rule exists:
'0/10' (participants / io.lotus.voice_limit) and/or a muted-camera glyph when
the room's io.lotus.room_quality forbids camera and screenshare; the tooltip
and aria-label carry the words ('Voice limit 10 (0 in call) · Audio-only
room'). Desktop only — the mobile header is already tight. Verified headless:
appears with the rules set, disappears when they are cleared.

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

src/app/features/room/RoomViewHeader.tsx

@@ -27,6 +27,8 @@ import {
 import { useAtom } from 'jotai';
 import { useNavigate } from 'react-router-dom';
 import { Room } from 'matrix-js-sdk';
+import { useVoiceChannelFull } from '../../hooks/useVoiceChannelFull';
+import { useRoomCallPolicy } from '../../hooks/useRoomCallPolicy';
 import { useStateEvent } from '../../hooks/useStateEvent';
 import { PageHeader } from '../../components/page';
 import { RoomAvatar, RoomIcon } from '../../components/room-avatar';
@@ -415,6 +417,54 @@ const CallMenu = forwardRef<HTMLDivElement, CallMenuProps>(
   },
 );
 
+/**
+ * [Gitea #134] One small chip that tells members a room's call rules before
+ * they hit the server-side guard: "8/10" when a voice limit is set, a muted
+ * camera glyph when the room is audio-only. Nothing when no rule exists; the
+ * tooltip carries the words. Desktop only (the mobile header is tight).
+ */
+function CallRulesChip({ room }: { room: Room }) {
+  const { current, max } = useVoiceChannelFull(room);
+  const { allowCamera, allowScreenshare } = useRoomCallPolicy(room);
+  const audioOnly = !allowCamera && !allowScreenshare;
+  if (max <= 0 && !audioOnly) return null;
+  const words = [
+    max > 0 ? `Voice limit ${max} (${current} in call)` : undefined,
+    audioOnly ? 'Audio-only room' : undefined,
+  ]
+    .filter(Boolean)
+    .join(' · ');
+  return (
+    <TooltipProvider
+      position="Bottom"
+      offset={4}
+      tooltip={
+        <Tooltip>
+          <Text>{words}</Text>
+        </Tooltip>
+      }
+    >
+      {(triggerRef) => (
+        <Chip
+          ref={triggerRef}
+          variant="Surface"
+          size="400"
+          radii="Pill"
+          aria-label={words}
+          tabIndex={0}
+          before={audioOnly ? <Icon size="50" src={Icons.VideoCameraMute} /> : undefined}
+        >
+          {max > 0 && (
+            <Text size="T200">
+              {current}/{max}
+            </Text>
+          )}
+        </Chip>
+      )}
+    </TooltipProvider>
+  );
+}
+
 function CallButton() {
   const room = useRoom();
   const direct = useIsDirectRoom();
@@ -731,6 +781,7 @@ export function RoomViewHeader({ callView }: { callView?: boolean }) {
                 </FocusTrap>
               }
             />
+            {screenSize === ScreenSize.Desktop && <CallRulesChip room={room} />}
             {!room.isCallRoom() &&
               livekitSupported &&
               rtcSupported &&