Protocol 11: sit out replaces kicking; nudge

Anyone can sit anyone out (host included); only you bring yourself back.
Out members stay in chat and the party, never block or count, and load no
media; a card with the live position and Join back (Space) replaces the
video. The mini player's x sits you out; optionally idle does too. Nudge:
the server forwards it to the target only (3/s, 20/min per sender); the
target hears the nudge sound, gets a toast and a taskbar attention
request. Kick, its messages, errors and dialog are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/server/lib/src/relay_routes.dart

@@ -139,13 +139,6 @@ class ActiveRelay {
     if (ch != null) unawaited(_closeNotSource(ch));
   }
 
-  /// Source member gone for good (kicked): stop its channel.
-  void dropChannel() {
-    final ch = _channel;
-    _channel = null;
-    if (ch != null) unawaited(_closeNotSource(ch));
-  }
-
   void _attachChannel(RelicWebSocket ws, List<int> sizes) {
     final old = _channel;
     if (old != null && !identical(old, ws)) unawaited(old.tryClose());
@@ -290,8 +283,6 @@ void mountRelayRoutes(
     switch (session.gate(token)) {
       case MediaGate.ok:
         break;
-      case MediaGate.forbidden:
-        return _plain(403);
       default:
         return _plain(401);
     }