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/notify.dart

@@ -0,0 +1,77 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+
+enum NotificationLevel { info, warning, error, success }
+
+@immutable
+class ClideNotification {
+  ClideNotification({
+    required this.id,
+    required this.level,
+    required this.message,
+    this.title,
+    this.duration = const Duration(seconds: 4),
+  }) : createdAt = DateTime.now().toUtc();
+
+  final String id;
+  final NotificationLevel level;
+  final String? title;
+  final String message;
+  final DateTime createdAt;
+  final Duration duration;
+}
+
+class Notifications extends ChangeNotifier {
+  final List<ClideNotification> _active = [];
+  final Map<String, Timer> _timers = {};
+  int _seq = 0;
+
+  List<ClideNotification> get active => List.unmodifiable(_active);
+
+  void info(String message, {String? title, Duration? duration}) =>
+      _push(NotificationLevel.info, message, title: title, duration: duration);
+  void warn(String message, {String? title, Duration? duration}) =>
+      _push(NotificationLevel.warning, message,
+          title: title, duration: duration);
+  void error(String message, {String? title, Duration? duration}) =>
+      _push(NotificationLevel.error, message, title: title, duration: duration);
+  void success(String message, {String? title, Duration? duration}) =>
+      _push(NotificationLevel.success, message,
+          title: title, duration: duration);
+
+  void dismiss(String id) {
+    _timers.remove(id)?.cancel();
+    final before = _active.length;
+    _active.removeWhere((n) => n.id == id);
+    if (_active.length != before) notifyListeners();
+  }
+
+  void _push(
+    NotificationLevel level,
+    String message, {
+    String? title,
+    Duration? duration,
+  }) {
+    final id = 'n${_seq++}';
+    final n = ClideNotification(
+      id: id,
+      level: level,
+      message: message,
+      title: title,
+      duration: duration ?? const Duration(seconds: 4),
+    );
+    _active.add(n);
+    _timers[id] = Timer(n.duration, () => dismiss(id));
+    notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    for (final t in _timers.values) {
+      t.cancel();
+    }
+    _timers.clear();
+    super.dispose();
+  }
+}