Add an Independent Review Step

A session that wrote the code is biased by its own context. For important work, add an independent review step.

Review prompt

Use a subagent to review the current diff against PLAN.md.
Check that every requirement is implemented, edge cases have tests,
and nothing outside the task scope changed.
Report correctness gaps, not style preferences.

What to review

• The current diff.
• The plan or acceptance criteria.
• Tests and verification output.
• Security or data handling risks.
• Scope creep.

Avoid over-reviewing

Ask the reviewer to report gaps that affect correctness or stated requirements. Otherwise it may generate low-value suggestions that lead to unnecessary abstraction or defensive code.