All three Cerebras entries (cerebras-gpt-oss-120b, cerebras-zai-glm-4.7,
cerebras-gemma-4-31b) returned HTTP 402 "Payment required" against a
standard account during the 0.12.0 audit pass. Whatever free tier
Cerebras previously offered is gone or restricted to specific plans.

Rather than ship entries that fail-closed for the average operator, drop
Cerebras from the bundled registry. Users on a paid Cerebras plan can
still add the models locally via `external-agents add-model
--provider cerebras ...` (see README) — the runtime supports any
OpenAI-compat endpoint, we just won't bundle Cerebras until a real
free tier reappears.

README's provider tile block claims "Cerebras 30 rpm, ~2000 tok/s" — no
longer true, will fix in a follow-up doc pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>