v0.37.12

A turn the provider refused says why, when the agent could not read the refusal

A Qwen Code turn refused by vLLM 0.10.0 or older failed with only "API Error: 400 status code (no body)". Qwen Code reads a refusal's reason only under an error key, and those vLLM versions put message at the top level, so the one thing a person could fix, a context window too small for the request, was never shown. The runner's relay had read vLLM's sentence all along.

A failed turn now gives the provider's own words whenever the reason it would otherwise show lacks them, for every agent harness whose calls go through the relay: The model provider refused the request (400: This model's maximum context length is 8192 tokens. However, you requested ...). An agent that already says the reason keeps its own sentence. Only the turn's last call counts: a refusal the relay repaired, or one before a call that went unanswered, is never given as a later failure's reason.

Thanks to @yuesu0202 (#614, #612).

Full Changelog: v0.37.11...v0.37.12