[ENHANCEMENT] Add dedicated API profile setting for commit generation #285

Problem (one or two sentences)

Users may want a small, fast, or cheaper model for commit-message generation instead of their active chat model.

Part of #145.

Context (who is affected and when)

Prompt enhancement already supports selecting a dedicated API profile, and commit-message generation should follow a similar pattern.

Desired behavior (conceptual, not technical)

Zoo can persist and resolve a commitMessageApiConfigId setting, falling back to the active provider when unset or invalid.

Constraints / preferences (optional)

The setting should be separate from enhancementApiConfigId.

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Zoo Code Task Links (optional)

No response

Optional (for contributors): You can stop here if you're just proposing the improvement.

Acceptance criteria (optional)

• commitMessageApiConfigId is added to global settings/types.
• The generator uses the selected profile when valid.
• The generator falls back to the active API config when unset, deleted, or invalid.
• Tests cover selected, unset, and invalid profile behavior.

Proposed approach (optional)

Add state/schema plumbing and generator profile resolution first; add visible settings UI in a separate issue.

Trade-offs / risks (optional)

Invalid or deleted profiles must not break commit generation when the active config is usable.