Restructure step 0 done: notice table test, flaky-link proxy, liveness on the engine clock, STARSYNC_PROFILE

- notice_table_test: one row per AppEvent variant through noticeFor.
- FlakyProxy (core/testing.dart): pass, blackhole (half-open), delay,
  hold, cut after N bytes, reset; demo tests against today's server.
- Liveness (stale/drop/ping) on the engine clock, so grace can be tested
  with a fake clock; Connection takes an injectable clock.
- AppDirs with STARSYNC_PROFILE=<name>: separate data and logs, so two
  instances run on one machine.
- DEVELOPMENT: scenario list per restructure step; test tags follow the
  new step order.

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

apps/desktop/lib/main.dart

@@ -7,6 +7,7 @@ import 'package:media_kit/media_kit.dart';
 import 'package:sync_relay_core/core.dart';
 
 import 'app.dart';
+import 'src/platform/app_dirs.dart';
 import 'src/platform/app_log.dart';
 import 'src/platform/app_shutdown.dart';
 import 'src/platform/desktop_entry.dart';
@@ -41,14 +42,17 @@ Future<void> main(List<String> args) async {
         ),
       );
   WidgetsFlutterBinding.ensureInitialized();
-  await startAppLogging();
-  await Hive.initFlutter();
+  final dirs = await AppDirs.resolve();
+  await startAppLogging(dirs);
+  // An absolute subDir replaces the documents folder (package:path join).
+  await Hive.initFlutter(dirs.hive);
   await AppSettings.instance.ensureLoaded();
   // Close button / Alt+F4: the orderly close ([shutDownApp]), so others
   // see "left", a hosted server shuts down and no player outlives the
   // engine.
   final ports = SessionState.instance.ports;
-  await ports.shell.start(title: appName, onCloseRequest: shutDownApp);
+  await ports.shell.start(
+      title: dirs.profile == null ? appName : '$appName [${dirs.profile}]', onCloseRequest: shutDownApp);
   try {
     await SessionState.instance.loadForm();
   } catch (e, st) {