OpenAI rejects desktop_clipboard_write top-level union schema on gpt-4.1-mini #192

Observed while smoke-checking queued-message UI for #24 in Ace, from main 4d503d3 plus the queue UI changes.

A real source worker using the existing OpenAI credential and model openai/gpt-4.1-mini rejects its first response with HTTP 400:

Invalid schema for function desktop_clipboard_write: schema must have type object and not have oneOf/anyOf/allOf/enum/const/not at the top level.

The request fails before any tool runs. The same queue smoke check succeeds with openai/gpt-6-astra. This is unrelated to the queue projection; that work leaves tool schemas untouched.

Please make the clipboard-write tool schema compatible with supported OpenAI models, or filter out models that cannot accept the shipped tool catalog. Dogfooding: #5.