refactor(yahweh): Fase 1 — nakui-ui-schema → yahweh-meta-schema

Primer paso del refactor yahweh. El schema de UI declarativa no
tiene acoplamiento real con Nakui (sólo dep en serde/thiserror) —
movemos a yahweh para que cualquier app metadata-driven lo use sin
pasar por nakui.

Mecánico:
- git mv crates/modules/nakui/ui-schema → crates/modules/ui_engine/libs/meta-schema.
- Crate name: nakui-ui-schema → yahweh-meta-schema.
- Workspace members[] actualizado (sección yahweh, no nakui).
- Consumers actualizados: brahman-cards (Cargo.toml + lib.rs +
  readers.rs), nakui-ui (Cargo.toml + main.rs).
- Self-test (example_modules.rs): import + path rebase (5 niveles
  arriba ahora).

Documental:
- Doc del crate ahora dice "metainterfaz (yahweh meta-schema)" +
  "backend-agnostic" en filosofía.
- Module.nakui_module_dir documentado como "path opaco al backend";
  se conserva el nombre por compat con módulos ya escritos +
  serde alias "backend_module_dir" para futuro rename suave.

Tests: 13 yahweh-meta-schema + 26 brahman-cards + 48 nakui-ui
verdes. Workspace build verde.

NO hace Fase 1: mover widgets a yahweh (Fase 2), trait MetaBackend
(Fase 3), renombrar nakui_module_dir.

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

Cargo.lock

@@ -1238,13 +1238,13 @@ name = "brahman-cards"
 version = "0.1.0"
 dependencies = [
  "brahman-card",
- "nakui-ui-schema",
  "nickel-lang",
  "nouser-card",
  "serde",
  "serde_json",
  "thiserror 2.0.18",
  "ulid",
+ "yahweh-meta-schema",
 ]
 
 [[package]]
@@ -6396,24 +6396,14 @@ dependencies = [
  "brahman-cards",
  "gpui",
  "nakui-core",
- "nakui-ui-schema",
  "serde_json",
  "tempfile",
  "uuid",
+ "yahweh-meta-schema",
  "yahweh-theme",
  "yahweh-widget-text-input",
 ]
 
-[[package]]
-name = "nakui-ui-schema"
-version = "0.1.0"
-dependencies = [
- "serde",
- "serde_json",
- "tempfile",
- "thiserror 2.0.18",
-]
-
 [[package]]
 name = "nanorand"
 version = "0.7.0"
@@ -12840,6 +12830,16 @@ dependencies = [
  "yahweh-theme",
 ]
 
+[[package]]
+name = "yahweh-meta-schema"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_json",
+ "tempfile",
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "yahweh-provider-fs"
 version = "0.1.0"