fix: inherit caller model in codex-rescue agent - #805

Fixes #804.

Summary

• Change codex-rescue agent frontmatter from model: sonnet to model: inherit.
• The agent is a thin forwarder that makes one Bash call to the Codex companion runtime. It does not need a specific Claude tier.
• A pinned alias resolves to one specific model ID. Organizations that restrict models see Model "..." is restricted by your organization's settings on every rescue, and the agent falls back to another model anyway. inherit runs it on the caller's model, which the user's organization already allows.
• A full model ID was considered, but it fails the same way for organizations that allow a different set, and it goes stale with each model release.

Testing

• npm test: 84 pass, 7 fail. The same 7 tests fail on main without this change (state dir, status, result and stop-hook tests), so they are unrelated to this change.
• Checked by hand: the frontmatter now reads model: inherit.