Diff review

Spec §20.3 / §21.3.2: a code-migration / tune-collab handoff is worthless without a human-reviewable diff. This atom is the "present the patch, capture the decision" stage.

Inputs

• The project cwd's accumulated edits since the run started (or since the previous diff-review iteration).
• plan/steps.json for context per file.

Output

project-cwd/
└── review/
    ├── diff.patch        # unified diff (git apply-shaped)
    ├── summary.md        # human-friendly per-file walkthrough
    ├── decision.json     # { decision: 'accept' | 'reject' | 'partial', accepted_files: [...], rejected_files: [...], reviewer: 'user' | 'agent' }
    └── meta.json         # { generatedAt, atomDigest, planRevision }

The atom raises a choice GenUI surface with the three top-level decisions (accept / reject / partial). On partial the user flips per-file decisions through follow-up surfaces.

Convergence

The atom completes when decision.json has a non-empty decision. Acceptance writes handoffKind: 'patch' (or 'deployable-app' when a successful build-test is on file) into the eventual artifact manifest; rejection rolls back the patch via `git rest…