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/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();
+}