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/adapter.dart

@@ -0,0 +1,30 @@
+import 'package:clide/extension/extension.dart';
+
+/// Tier-0 stub. The real adapter wraps a parsed Lua extension manifest
+/// and a handle to the Lua state; contributions are proxied to
+/// callbacks registered by `clide.contribute(...)` from the Lua side.
+class LuaExtension extends ClideExtension {
+  LuaExtension({
+    required this.id,
+    required this.title,
+    required this.version,
+    this.dependsOn = const [],
+  });
+
+  @override
+  final String id;
+  @override
+  final String title;
+  @override
+  final String version;
+  @override
+  final List<String> dependsOn;
+
+  @override
+  List<ContributionPoint> get contributions => const [];
+
+  @override
+  Future<void> activate(ClideExtensionContext ctx) async {
+    throw UnsupportedError('Lua runtime lands at Tier 6.');
+  }
+}

lib/lua/src/capability_api.dart

@@ -0,0 +1,13 @@
+/// Tier-0 stub for the sandboxed `clide.*` table exposed to third-party
+/// Lua extensions.
+///
+/// The surface is deliberately narrow: `clide.ipc.request`,
+/// `clide.events.on`, `clide.log`, `clide.contribute`, and scoped
+/// kernel-service getters that mirror `ClideExtensionContext`. Lua
+/// code has no `io`, no `os.execute`, no `package.loadlib`, no `debug`
+/// — those are removed from the global state at sandbox init.
+///
+/// Full binding table lands with the Lua runtime at Tier 6.
+class CapabilityApi {
+  const CapabilityApi();
+}

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 {}
+}

lib/lua/src/render_intent.dart

@@ -0,0 +1,14 @@
+/// Tier-0 stub for the declarative widget DSL Lua extensions return
+/// from their `on_render` callbacks.
+///
+/// Lua can't construct Flutter widgets; instead it returns tables like
+/// `{type="list", items={...}}` or `{type="stack", children={...}}`,
+/// which the Dart renderer maps to widget primitives. The vocabulary
+/// is closed and documented — extensions declare intent, the shell
+/// renders it with consistent theming.
+///
+/// The concrete intent shapes (list, tree, stack, button, text, input,
+/// editor-embed) land with the Lua adapter at Tier 6.
+sealed class RenderIntent {
+  const RenderIntent();
+}