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/lua/src/host.dart

@@ -0,0 +1,14 @@
+/// Tier-0 stub. The real implementation loads a vendored liblua via
+/// `dart:ffi` and exposes a `LuaState` handle that [LuaExtension] uses
+/// to run script callbacks. Lands at Tier 6.
+class LuaHost {
+  LuaHost._();
+
+  /// Boot the vendored liblua. Throws until Tier 6.
+  static Future<LuaHost> start() async {
+    throw UnsupportedError(
+        'Lua runtime lands at Tier 6 (supporter tool sibling of ptyc).');
+  }
+
+  Future<void> dispose() async {}
+}