scaffold Flutter app — kernel, extensions, widgets, Tier 0 built-ins

First real content under app/. Lays the whole Tier 0 foundation in one
commit because the pieces depend on each other circularly (kernel →
extension → widgets → built-ins all reference types from the layer
below); splitting would leave intermediate commits that don't compile.

Key shapes:

  * bare WidgetsApp root — no Material, no Cupertino, no Scaffold.
    ClideTheme InheritedWidget is the only source of tokens.
  * ClideKernel InheritedWidget aggregates 18 services (settings,
    project, extensions, theme, panels, events, ipc, commands +
    palette + keybindings, clipboard, files, notify, dialog, tray,
    secrets, os, net, focus, log, i18n). ExtensionContext exposes
    them through a stable interface.
  * ClideExtension + sealed ContributionPoint hierarchy (Tab,
    StatusItem, Toolbar, Command, TrayItem, LayoutPreset). One
    manifest ships N contributions into kernel slots.
  * Three-tier theme pipeline: palette (named colors) → semantic
    roles → ~60 surface tokens. Defaults at each layer so legacy
    palette-only themes produce a complete SurfaceTokens.
  * A11y baked in from day one — every interactive primitive wraps
    in Semantics(label:, hint:, button:); ensureSemantics() at boot;
    theme/contrast.dart helper exposes token pairs for the WCAG
    gate in the a11y test suite.
  * i18n ported from fframe's L10n pattern (text-driven, namespaced
    JSON catalogs, caller-supplied placeholders) with a proper
    locale fallback chain (exact → language → default → placeholder)
    fframe lacks.
  * Four Tier-0 built-ins live (default-layout, welcome, ipc-status,
    theme-picker) plus 17 id-reserving stubs so later tiers fill in
    without rename churn.

.gitignore extended to cover app/ sub-package artefacts and the
Playwright harness scratch dirs.

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

app/lib/kernel/src/events/bus.dart

@@ -0,0 +1,22 @@
+import 'dart:async';
+
+import 'package:clide_app/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();
+}

app/lib/kernel/src/events/types.dart

@@ -0,0 +1,112 @@
+import 'package:flutter/foundation.dart';
+
+@immutable
+abstract class ClideEvent {
+  const ClideEvent();
+
+  String get subsystem;
+  String get kind;
+
+  Map<String, Object?> payload() => const {};
+}
+
+@immutable
+class ClideEventEnvelope {
+  const ClideEventEnvelope(this.event, this.timestamp);
+
+  final ClideEvent event;
+  final DateTime timestamp;
+
+  Map<String, Object?> toJson() => {
+        'v': 1,
+        'subsystem': event.subsystem,
+        'kind': event.kind,
+        'ts': timestamp.toIso8601String(),
+        'data': event.payload(),
+      };
+}
+
+class DaemonConnectionChanged extends ClideEvent {
+  const DaemonConnectionChanged({required this.connected});
+  final bool connected;
+  @override
+  String get subsystem => 'ipc';
+  @override
+  String get kind => 'connection-changed';
+  @override
+  Map<String, Object?> payload() => {'connected': connected};
+}
+
+class ThemeChanged extends ClideEvent {
+  const ThemeChanged({required this.themeName});
+  final String themeName;
+  @override
+  String get subsystem => 'theme';
+  @override
+  String get kind => 'changed';
+  @override
+  Map<String, Object?> payload() => {'theme': themeName};
+}
+
+class ProjectOpened extends ClideEvent {
+  const ProjectOpened({required this.path});
+  final String path;
+  @override
+  String get subsystem => 'project';
+  @override
+  String get kind => 'opened';
+  @override
+  Map<String, Object?> payload() => {'path': path};
+}
+
+class ProjectClosed extends ClideEvent {
+  const ProjectClosed();
+  @override
+  String get subsystem => 'project';
+  @override
+  String get kind => 'closed';
+}
+
+class ExtensionActivated extends ClideEvent {
+  const ExtensionActivated({required this.id});
+  final String id;
+  @override
+  String get subsystem => 'extensions';
+  @override
+  String get kind => 'activated';
+  @override
+  Map<String, Object?> payload() => {'id': id};
+}
+
+class ExtensionDeactivated extends ClideEvent {
+  const ExtensionDeactivated({required this.id});
+  final String id;
+  @override
+  String get subsystem => 'extensions';
+  @override
+  String get kind => 'deactivated';
+  @override
+  Map<String, Object?> payload() => {'id': id};
+}
+
+/// Forwarded from the daemon. Feature extensions subscribe to this and
+/// narrow by subsystem+kind, or register a converter that emits a typed
+/// `ClideEvent` subclass into the bus.
+class DaemonEvent extends ClideEvent {
+  const DaemonEvent({
+    required this.subsystem,
+    required this.kind,
+    required this.data,
+    required this.ts,
+  });
+
+  @override
+  final String subsystem;
+  @override
+  final String kind;
+  final Map<String, Object?> data;
+  final DateTime ts;
+
+  @override
+  Map<String, Object?> payload() => {'ts': ts.toIso8601String(), ...data};
+}