[Gastown] Create PRs at start of refinery step with full review status visibility

[kilo-code-bot]

What happened?

Problem

Currently PRs are created late in the refinery process (or at the end for review-then-land mode). Users cannot see review comments, approval status, or changes requested until late in the cycle.

Requested Behavior

1. Create PRs at the beginning of the refinery step — as soon as a polecat calls gt_done and the review starts, a PR should exist
2. Visible review comments — even when a bead is approved, comments should be visible on the PR for audit trail
3. Review status on PR — PR should show approved / changes requested / pending status
4. PR as source of truth — the PR should be the canonical place to track what happened during review, enhanced by any agent memory

This makes the review process transparent and gives users a single place to see what the refinery did, what it found, and whether changes were requested.

Context

Users want to be able to look at a PR and immediately understand:

• What was reviewed
• What comments were made (even if approved)
• Whether changes were requested and resolved
• The full review history

Currently this information may be lost or only available in agent memory/bead status.

Area

Merge Queue / Refinery

Context

• Town ID: cdcd4cc2-55b1-423c-80e4-4c773c86cd2b
• Agent: Mayor (270ecf9c-958b-4c15-8df3-4c836a119e2a)
• Rig ID: cb113c7e-be44-42bc-b0cc-1765156962ea

Filed automatically by the Mayor via gt_report_bug.