更完

docs/CORE_GUIDE.md

@@ -56,6 +56,32 @@ struct structive::Type_Descriptor<Device> {
 
 The descriptor is the structural definition of `Device`.
 
+### 3.1 Type-level metadata
+
+Extensions can attach compile-time attributes to the described type itself, independently
+from property metadata and inheritable property defaults:
+
+```cpp
+struct Action_Category {};
+struct Action {
+    using attribute_category = Action_Category;
+    static constexpr bool single_valued = false;
+    static constexpr bool inheritable = false;
+    std::string_view name;
+};
+
+return object<Device>(
+    type_metadata(Action{"reset"}, Action{"calibrate"}),
+    field<&Device::temperature>(key<"temperature">)
+);
+```
+
+Use `Schema::type_attribute_count<Category>`, `Schema::has_type_attribute<Category>`,
+`schema.type_attribute<Category>()` for a single-valued category, and
+`schema.for_each_type_attribute<Category>(callback)` for traversal. Core stores and
+validates the generic Attribute protocol but does not interpret extension-owned categories.
+Type metadata is not a property default and is never copied into individual properties.
+
 ## 4. Schema guarantees
 
 A valid schema guarantees: