a Driver Fix Diff

<!-- Orchestrator contract:
  role: driver
  reads: [DIFF_REVIEW_NOTES.md, REREVIEW_NOTES.md, PLAN.md, TASK_QUEUE.md, NOW.md]
  writes: [TASK_QUEUE.md, NOW.md, DIFF_SUMMARY.md, FIX_SUMMARY.md, DECISIONS.md]
  never_writes: [DIFF_REVIEW_NOTES.md, REVIEW_NOTES.md, REREVIEW_NOTES.md]
  produces: [STEP_RESULT.json]
-->
# 4a. Driver — Fix Diff Review Blockers

You are in Driver mode.

Resolve active slice: Read ROADMAP.md -> find "Current Active Slice" -> use as `changes/<slug>/`.

Read:
- `changes/<slug>/DIFF_REVIEW_NOTES.md`
- `changes/<slug>/REREVIEW_NOTES.md` if present (latest reviewer direction)

Goal:
Apply reviewer-requested fixes with minimal scope changes. Reviewer owns verdict transitions.

## Fix pass
1) Implement all unresolved structural blockers.
2) Implement local issues required before PR.
3) Add missing tests requested by reviewer.
4) If you disagree with a finding, document rationale in `DECISIONS.md` (do not silently skip).
5) Keep scope stable; no unrelated refactors.

## Required outputs
- Update `TASK_QUEUE.md` statuses.
- Update `NOW.md` (max 3 items).
- Append `DIFF_SUMMARY.md` with files/behavior changes.
- Update `FIX_SUMMARY.md`:
  - blockers addressed
  - local issues addressed/deferred
  - files changed
  - impact checkboxes
  - `Re-review required: YES | NO`
- Update `DECISIONS.md` only when needed.

Do not edit reviewer files (`DIFF_REVIEW_NOTES.md`, `REREVIEW_NOTES.md`).

## Output checklist (non-negotiable)
- [ ] `changes/<slug>/TASK_QUEUE.md`
- [ ] `changes/<slug>/NOW.md`
- [ ] `changes/<slug>/DIFF_SUMMARY.md`
- [ ] `changes/<slug>/FIX_SUMMARY.md`
- [ ] `changes/<slug>/DECISIONS.md` (if needed)
- [ ] `changes/<slug>/STEP_RESULT.json`

## STEP_RESULT.json (required)

Write `changes/<slug>/STEP_RESULT.json`: