Confirm merged fixes on the real Coder setup #234

These fixes are merged and tested locally (mocks and the live harness), but haven't been confirmed against the real Coder deployment:

• Claude text generation (titles, branch names, commit and MR text) with a claude wrapper that prints a banner to stdout before the JSON — PR Let Claude text generation read past a workspace launcher's banner #213.
• Review guides with Claude, which share that text-generation runner — PR Let Claude text generation read past a workspace launcher's banner #213.
• Pi text generation with models registered by a Pi extension (extensions stay loaded) — PR Load workspace Pi extensions for Pi text generation #209.
• Opening a merge request link on a self-hosted GitLab host without "gitlab" in its name — PR Drop the fork-only merge request link host check #199.

Tick each item once checked, and open a separate bug for anything that still fails.