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/lua.dart

@@ -0,0 +1,13 @@
+/// Lua extension runtime boundary (Tier 6 impl; Tier 0 stubs only).
+///
+/// Third-party extensions run in a vendored `liblua` loaded via
+/// `dart:ffi`, sandboxed to a narrow `clide.*` capability API, and
+/// render via a declarative widget-intent DSL. The `LuaExtension`
+/// adapter proxies to the Lua state so Lua extensions implement the
+/// same `ClideExtension` contract as Dart built-ins.
+library;
+
+export 'src/adapter.dart';
+export 'src/capability_api.dart';
+export 'src/host.dart';
+export 'src/render_intent.dart';