split EventBus into DaemonBus + MessageBus

DaemonBus (was EventBus): typed events for system/IPC layer.
MessageBus: channel-based pub/sub for UI/extension coordination.
Messages carry publisher (auto-stamped from extension ID),
channel (required), timestamp, and payload. Subscribe by
publisher, channel, or both — zero collision across extensions.

Extension context gains publish() and subscribe() convenience
methods that auto-stamp the extension's ID as publisher.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/kernel/src/project.dart

@@ -45,14 +45,14 @@ class RecentProject {
 class ProjectManager extends ChangeNotifier {
   ProjectManager({
     required Logger log,
-    required EventBus events,
+    required DaemonBus events,
     required SettingsStore settings,
   })  : _log = log,
         _events = events,
         _settings = settings;
 
   final Logger _log;
-  final EventBus _events;
+  final DaemonBus _events;
   final SettingsStore _settings;
 
   Directory? _current;