fix(optional): convert Optional[T] returns to T | None syntax; regen type registry

docs/type_registry/src_openai_schemas.md

@@ -30,7 +30,7 @@ Auto-generated from source. 6 struct(s) defined in this module.
 ## `src\openai_schemas.py::OpenAICompatibleRequest`
 
 **Kind:** `dataclass`
-**Defined at:** line 120
+**Defined at:** line 97
 
 **Fields:**
 - `messages: list[ChatMessage]`

docs/type_registry/src_provider_state.md

@@ -5,7 +5,7 @@ Auto-generated from source. 1 struct(s) defined in this module.
 ## `src\provider_state.py::ProviderHistory`
 
 **Kind:** `dataclass`
-**Defined at:** line 26
+**Defined at:** line 27
 
 **Fields:**
 - `messages: list[HistoryMessage]`