dissolve app/ into repo root (D-056)

Single Flutter package at the repo root. All code, tests, assets,
and platform directories moved from app/ to root. Package renamed
from clide_app to clide — all imports rewritten. Merged pubspec
combines core (ffi) and app (flutter, yaml, xterm) dependencies.
Makefile simplified: no APP_PRESENT conditionals, no cd, no daemon
lifecycle. 317 tests pass.

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

lib/kernel/src/events/bus.dart

@@ -0,0 +1,22 @@
+import 'dart:async';
+
+import 'package:clide/kernel/src/events/types.dart';
+
+class EventBus {
+  EventBus();
+
+  final StreamController<ClideEventEnvelope> _controller =
+      StreamController<ClideEventEnvelope>.broadcast();
+
+  Stream<ClideEventEnvelope> get stream => _controller.stream;
+
+  Stream<T> on<T extends ClideEvent>() =>
+      _controller.stream.where((e) => e.event is T).map((e) => e.event as T);
+
+  void emit(ClideEvent event) {
+    if (_controller.isClosed) return;
+    _controller.add(ClideEventEnvelope(event, DateTime.now().toUtc()));
+  }
+
+  Future<void> dispose() => _controller.close();
+}