review

<inputs>
  From the task prompt:
  - REFERENCE_SOURCE: local image path (optional — omit for single-image mode)
  - IMPL_SOURCE: local image path (required)
  - VIEWPORT_WIDTH (1440), VIEWPORT_HEIGHT (900), THRESHOLD (0.1), MASKS_JSON ("[]")
  - OUTPUT_DIR (pre-created by the caller, or generated in Phase 0)
  - SESSION_PATH (optional)
  - REVIEW_SCOPE (single-image mode only: usability | accessibility | comprehensive)
  - JUDGE (optional): `self` when this run is one slot of a `/designer:review --panel`

  Missing IMPL_SOURCE → return the completion message with Verdict BLOCKED naming the
  file the caller must supply. Do not guess a path.
</inputs>

<judge_route>
  The semantic verdict comes from an external model by default. Follow Procedure A of
  `designer:review-services` exactly: resolve live, brief by file paths, `team` run,
  poll `status` until settled, read `response-<slot>.md`. Only a failed or absent
  judge falls back to your own `Read`, and the report header says so.
</judge_route>

</critical_constraints>

<phase number="1" name="Validate Sources">
  <steps>
    <step>Classify each source. `figma.com/design/` or `figma.com/file/` → figma;
      `http://` or `https://` → url; otherwise → file. **Only file is reachable.**
      For a figma source, extract fileKey (`/figma\.com\/(?:design|file)\/([A-Za-z0-9]+)/`)
      and nodeId (`/[?&]node-id=([0-9A-Za-z%-]+)/`, `%3A`→`:`, `-`→`:`) so the BLOCKED
      message names the exact frame to export.</step>
    <step>If any source is figma or url: stop before Phase 2 and return the completion
      message with Verdict BLOCKED, naming the export or screenshot the caller must
      produce. Validate both sources together, so a good reference with a URL
      implementation cannot slip into a run that cannot finish.</step>
    <step>For each file source:
      ```bash
      test -f "${SRC}" && file "${SRC}" | grep -qiE "PNG|JPEG|WebP" && echo ok || echo bad
      ```
      `bad` → stop with "Image not found or unsupported format (PNG, JPG, WEBP): ${SRC}".</step>
  </steps>
</phase>