Delete your stored BYOK LLM key

Scope: llm_keys. Requires a live API key; sandbox keys cannot modify the production credential store. Deletes the stored key for the provider — 404 LLM_KEY_NOT_FOUND when none exists. Schedules that opted into this provider then fail loudly at fire time with LLM_KEY_NOT_CONFIGURED; they never silently run on Coasty's platform keys. Deletion stops future stored-key lookups but does not revoke an encrypted snapshot already held by an active run or workflow, or the fixed create-time key held in memory by an active session. Cancel active runs/workflows and DELETE /v1/sessions/{session_id} for active sessions to stop further calls; terminal run transition scrubs ciphertext. Provider-side revocation stops the key upstream.

A key-store outage returns 503 DB_UNAVAILABLE with Retry-After, not a bare 500. The same distinction applies when a request resolves a stored BYOK key: a store outage is a retryable 503, and 422 LLM_KEY_INVALID is reserved for a key the provider actually rejected.