feat: add interactive maintainer source review - #263

🎯 Changes

Stacked on #262. Adds intent maintainer review --interactive for maintainers who want to inspect and record source-review decisions without editing a JSON report.

• Inspect current guidance and Git changes per item, then record an outcome, reason, and actual evidence or leave the item pending.
• Show the proposed outcomes before confirmation. Cancellation writes no review state.
• Record through the existing fingerprint and evidence checks. Source changes during the interaction invalidate the affected decisions.
• Preserve JSON reporting and recording for agents and automation. Interactive mode fails in CI; maintainer check remains the read-only gate.

Documentation is in #259, not this PR. The interaction stores supplied evidence; it does not execute evidence strings or judge whether a conclusion is correct.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).