- Classic PromptManager/PromptManagerText expose _pmTextSerializerReady, settled
once their own text serializer is installed; the real-host specs wait on it
and assert the Classic text is queued as written, as on main.
- The Primitive fill only touches an output entry whose class_type matches the
graph node at that id.
- TESTING.md notes the host's harmless "Invalid widget" warning per Run.