Protocol 15: one shared session log on the server, chat never logged, Mark a problem

Every app streams its redacted diagnostic lines (server time, batched
every 10 s, gzip, buffered while offline) to POST /l/; the server merges
them with its own into session-YYYY-MM-DD.log in time order, tagged by
who. Opt-out in Settings > About; Mark a problem (Ctrl+Shift+B, the
player menus, About) writes a marker with an optional note. Copy
diagnostics can include the server's session log. Chat text never
reaches any log.

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

packages/server/lib/src/serve.dart

@@ -19,7 +19,8 @@ import 'sync_server.dart';
 /// swap; a following `swap` with its name and size puts it up) and answers
 /// `{'ok':true,'name':n,'size':s}` or `{'ok':false}`. Without [events] a
 /// start failure throws. `'loopbackOnly': true` in [config] (next to the
-/// [AppConfig] keys) binds 127.0.0.1 only: the app's solo session.
+/// [AppConfig] keys) binds 127.0.0.1 only: the app's solo session;
+/// `'logDir'` is the folder of the session log ([SyncServer.logDir]).
 Future<void> serve(Map<String, Object?> config, {SendPort? events}) async {
   StreamSubscription<pkg_logging.LogRecord>? logs;
   if (events != null) {
@@ -34,7 +35,9 @@ Future<void> serve(Map<String, Object?> config, {SendPort? events}) async {
   }
   final SyncServer server;
   try {
-    server = SyncServer(AppConfig.fromMap(config), loopbackOnly: config['loopbackOnly'] == true);
+    final logDir = config['logDir'];
+    server = SyncServer(AppConfig.fromMap(config),
+        loopbackOnly: config['loopbackOnly'] == true, logDir: logDir is String && logDir.isNotEmpty ? logDir : null);
     await server.start();
   } catch (e) {
     await logs?.cancel();