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/commands/palette.dart

@@ -0,0 +1,50 @@
+import 'package:clide/extension/src/contribution.dart';
+import 'package:clide/kernel/src/commands/registry.dart';
+import 'package:flutter/foundation.dart';
+
+class PaletteController extends ChangeNotifier {
+  PaletteController(this._registry);
+
+  final CommandRegistry _registry;
+
+  bool _open = false;
+  String _filter = '';
+
+  bool get isOpen => _open;
+  String get filter => _filter;
+
+  void open() {
+    if (_open) return;
+    _open = true;
+    notifyListeners();
+  }
+
+  void close() {
+    if (!_open) return;
+    _open = false;
+    _filter = '';
+    notifyListeners();
+  }
+
+  void toggle() => _open ? close() : open();
+
+  void setFilter(String f) {
+    if (_filter == f) return;
+    _filter = f;
+    notifyListeners();
+  }
+
+  List<CommandContribution> filtered() {
+    if (_filter.isEmpty) return _registry.all.toList();
+    final q = _filter.toLowerCase();
+    return _registry.all.where((c) {
+      final haystack = (c.title ?? c.command).toLowerCase();
+      return haystack.contains(q);
+    }).toList();
+  }
+
+  Future<void> invoke(String command) async {
+    close();
+    await _registry.execute(command);
+  }
+}