chore(z-ai): retire harness — no active subscription

Removes harnesses/contexts/z-ai/v1/. Mirrors the agent-runtimes
companion PR — the z-ai harness was never cut over to ESO and
there's no active subscription. Revival path documented in
agent-runtimes planning/future/providers F49.

Removed:
- harnesses/contexts/z-ai/v1/{harness.yaml, init.sh}

Updated:
- CLAUDE.md — drops z-ai from the 'no secrets in this repo'
  context list. Retirement note added.
- gitea-admin/v1/init.sh — comment ref to z-ai removed.
- gitea-https/v1/init.sh — comment ref to z-ai removed.

No composites layer z-ai (verified via grep across composites/);
no model registry entries reference it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -99,7 +99,7 @@ layers:
 
 ### No secrets in this repo
 
-This is a public framework repo. Secrets (provider API keys, SOPS-encrypted env files) belong in per-installation private repos attached at a lower CRS priority. The `z-ai/v1`, `minimax/v1`, `alibaba-model-studio/v1` contexts here declare the structure but leave `provider.sops.env` to the installation repo.
+This is a public framework repo. Secrets (provider API keys) live in OpenBao via M22 ESO, never in the framework. The `minimax/v1` context here declares the structure; the live credential is mounted by ESO from the per-installation OpenBao instance. (Z.ai and Alibaba Model Studio contexts are retired but revivable — see agent-runtimes `planning/future/providers` F49 / F50.)
 
 ## Adding a New Harness Context