The credential pool seeder and runtime credential resolver hardcoded
api.z.ai/api/paas/v4 for all Z.AI keys. Keys on the Coding Plan (or CN
endpoint) would hit the wrong endpoint, causing 401/429 errors on the
first request even though a working endpoint exists.
Add _resolve_zai_base_url() that:
- Respects GLM_BASE_URL env var (no probe when explicitly set)
- Probes all candidate endpoints (global, cn, coding-global, coding-cn)
via detect_zai_endpoint() to find one that returns HTTP 200
- Caches the detected endpoint in provider state (auth.json) keyed on
a SHA-256 hash of the API key so subsequent starts skip the probe
- Falls back to the default URL if all probes fail
Wire into both _seed_from_env() in the credential pool and
resolve_api_key_provider_credentials() in the runtime resolver,
matching the pattern from the kimi-coding fix (PR #5566).
Fixes the same class of bug as #5561 but for the zai provider.
9e844160f9