Generic plugin-OAuth support that the Solstice provider needs. None of it
names a provider:
- OAuthPKCEConfig.token_request: a confidential client whose secret lives
behind a broker hands the grant to the plugin in place of a token_url
POST. The old refresh_token is kept when the response omits one, which
Google does on refresh.
- Plugin OAuth rows rotate 2 minutes ahead of their stored expires_at_ms
(shared with the anthropic rule). Opaque bearers such as Google's ya29.*
carry no JWT exp, so this stored expiry is the only clock they have.
- A row whose refresh grant just went DEAD stays DEAD on the inference 401
that follows; before this it was re-benched EXHAUSTED and the dead token
was replayed every cooldown.
- The auxiliary client serves an OAuth plugin that ships create_client from
its pooled row on the main runtime's endpoint (compression, titles). It
used to return "not directly supported".
- A 401 on a plugin OAuth row prints a re-sign-in hint, not the API-key
advice.
- The Gemini native adapter exposes its method names, auth headers and
error builder so a Bearer-auth subclass can reuse it without the API-key
remedies.
f12e6b66d9