refactor(yahweh): Fase 2c — widget render extraído a yahweh-widget-meta-form

Cierra el refactor de UI. El widget render (forms, lists, modal de
delete, EntityRef selector, sidebar, key handlers) deja de vivir en
nakui-ui y pasa a un crate yahweh nuevo, genérico sobre MetaBackend.

crates/modules/ui_engine/widgets/meta-form/ (yahweh-widget-meta-form):
- pub MetaApp<B: MetaBackend> con todo el state UI + impl Render
  + handlers + render_*. El bound `B: MetaBackend` se propaga.
- pub fn new(modules, backend, initial_toast, initial_error, cx):
  constructor sin bootstrap. Caller pre-construye todo.
- Helpers locales del widget: lookup_field, append_compact_msg,
  format_seed_toast.
- Cero deps a nakui o brahman-cards. Reusable por cualquier app.
- 3 tests funcionales puros (lookup_field, append_compact_msg,
  format_seed_toast).

nakui-ui (shell):
- main.rs: 1959 → 424 líneas (78% reducción). Sólo bootstrap:
  load_ui_modules + load executors + NakuiBackend::open +
  cx.open_window con MetaApp::<NakuiBackend>::new como root view.
- Dep nueva yahweh-widget-meta-form.
- Tests E2E quedan: event_log_replay, morphism_pipeline real
  sales, load_ui_modules x3 (4 shell). NakuiBackend tests siguen
  en backend.rs (8). Widget tests en su crate.

Distribución total tests refactor yahweh:
- yahweh-meta-schema: 8
- yahweh-meta-runtime: 42
- yahweh-widget-meta-form: 3
- brahman-cards: 26
- nakui-ui: 12 (4 shell + 8 backend)
Total: 91 tests cubriendo el área.

Cada crate compila individualmente. Fase 3 (shell mínimo) era
implícita en F2c — el shell ya quedó en 424 líneas.

Pendientes restantes: KCL → Nickel, eliminar card.k.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/apps/nakui-ui/Cargo.toml

@@ -11,6 +11,7 @@ yahweh-meta-schema = { path = "../../modules/ui_engine/libs/meta-schema" }
 yahweh-meta-runtime = { path = "../../modules/ui_engine/libs/meta-runtime" }
 brahman-cards = { path = "../../core/brahman-cards" }
 yahweh-widget-text-input = { path = "../../modules/ui_engine/widgets/text_input" }
+yahweh-widget-meta-form = { path = "../../modules/ui_engine/widgets/meta-form" }
 yahweh-theme = { path = "../../modules/ui_engine/libs/theme" }
 gpui = { workspace = true }
 serde_json = { workspace = true }

crates/modules/ui_engine/widgets/meta-form/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "yahweh-widget-meta-form"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+description = "Yahweh — widget metainterfaz: lista, formulario, modal de delete y selector EntityRef que renderean cualquier `yahweh-meta-schema::Module` contra cualquier `yahweh_meta_runtime::MetaBackend`. App-agnostic."
+
+[dependencies]
+gpui = { workspace = true }
+serde_json = { workspace = true }
+uuid = { workspace = true, features = ["serde"] }
+yahweh-meta-runtime = { path = "../../libs/meta-runtime" }
+yahweh-meta-schema = { path = "../../libs/meta-schema" }
+yahweh-theme = { path = "../../libs/theme" }
+yahweh-widget-text-input = { path = "../text_input" }