Gate‑C(Core) OOB strict fail‑fast; String VM handler normalization; JSON lint Stage‑B root fixes via scanner field boxing and BinOp operand slotify; docs + smokes update

src/runtime/mod.rs

@@ -19,6 +19,7 @@ pub mod semantics;
 pub mod unified_registry;
 pub mod provider_lock;
 pub mod provider_verify;
+pub mod observe; // Lightweight observability flags (OOB etc.)
 // pub mod plugin_box;  // legacy - 古いPluginBox
 // pub mod plugin_loader;  // legacy - Host VTable使用
 pub mod extern_registry; // ExternCall (env.*) 登録・診断用レジストリ