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/net.dart

@@ -0,0 +1,18 @@
+import 'package:flutter/foundation.dart';
+
+enum Reachability { online, offline, metered }
+
+/// Tier-0 stub reachability observable. Hardcoded to `online`; real
+/// detection via a platform channel lands in a later tier.
+class NetworkStatus extends ChangeNotifier {
+  Reachability _state = Reachability.online;
+  Reachability get state => _state;
+  bool get isOnline => _state != Reachability.offline;
+
+  @visibleForTesting
+  void setState(Reachability r) {
+    if (_state == r) return;
+    _state = r;
+    notifyListeners();
+  }
+}