Add cerebras as a built-in OpenAI-compatible alias provider, following the
groq/deepseek pattern. Registers the alias (base URL https://api.cerebras.ai/v1,
token CEREBRAS_API_KEY), auto-detection in cloudProviders, default model
gpt-oss-120b, schema and docs updates, an example config, and unit tests.
Unlike DeepSeek (a first-party API with a fixed model lineup), Cerebras fronts
open-weight models such as GPT-OSS and GLM whose chat templates may only accept
a single leading system message. It is therefore added to openModelHostProviders
so docker-agent coalesces its per-source system messages (agent instruction plus
each toolset's instruction) into one, as already done for baseten, ovhcloud,
openrouter, and nebius (issues #3344, #2327).
The default gpt-oss-120b is present in the embedded models.dev snapshot, so
capability detection resolves out of the box.
Also adds an end-to-end test that drives a real HTTP request through the full
stack against a local OpenAI-compatible server, plus a CEREBRAS_API_KEY-gated
live API test.
Closes#3350
Sayt-0
5d400aad56