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/session.dart

@@ -3,21 +3,31 @@ import 'dart:math';
 
 import 'package:sync_relay_core/core.dart';
 
-enum MediaGate { ok, gone, unauthorized, forbidden, offline }
+enum MediaGate { ok, gone, unauthorized, offline }
 
 class ViewerToken {
   final String token;
   /// Cleaned ([cleanMemberName]); follows `profile` renames.
   String name;
-  bool kicked = false;
   /// Sent the server's host key in hello: the hosting app's own client.
   bool isHost = false;
   int bytesServed = 0;
   DateTime lastSeen;
-  Future<void> Function(String reason)? onKick;
+  /// When this member's recent nudges went out, for the rate cap.
+  final List<DateTime> nudges = [];
   ViewerToken({required this.token, required this.name})
       : lastSeen = DateTime.now().toUtc();
 
+  /// Takes one nudge at [now] if under the caps
+  /// ([RelayConstants.nudgesPerSec] / [RelayConstants.nudgesPerMin]).
+  bool takeNudge(DateTime now) {
+    nudges.removeWhere((t) => now.difference(t) >= const Duration(minutes: 1));
+    final lastSec = nudges.where((t) => now.difference(t) < const Duration(seconds: 1)).length;
+    if (nudges.length >= RelayConstants.nudgesPerMin || lastSec >= RelayConstants.nudgesPerSec) return false;
+    nudges.add(now);
+    return true;
+  }
+
   bool isStale(Duration timeout, [DateTime? now]) =>
       (now ?? DateTime.now().toUtc()).difference(lastSeen) > timeout;
 
@@ -66,17 +76,9 @@ class Session {
 
   MediaGate gate(String? token) {
     if (token == null || !tokens.containsKey(token)) return MediaGate.unauthorized;
-    if (tokens[token]!.kicked) return MediaGate.forbidden;
     return MediaGate.ok;
   }
 
-  Future<void> kick(String token, {String reason = ''}) async {
-    final viewer = tokens[token];
-    if (viewer == null) throw const AuthException('unknown token');
-    viewer.kicked = true;
-    await viewer.onKick?.call(reason);
-  }
-
   void addBytes(String? token, int n) {
     if (token != null) tokens[token]?.bytesServed += n;
   }