Finalize Step: review-retrospective

Purpose

After a plan finishes, compare the PR's reviewers — the two automated reviewers (CodeRabbit coderabbitai, Gemini Code Assist gemini-code-assist) plus any human reviewer — on review quality, reading THIS plan's pr-comment findings grouped by reviewer. The step is HYBRID by construction:

• A deterministic numbers pass (the backing review_retrospective.py aggregator) computes the per-reviewer, (author, kind)-grouped metrics. These counts are authoritative and are NOT recomputed by the LLM.
• An LLM qualitative-judgment pass (this workflow body) reads the comment titles/bodies/details + their resolutions + the deterministic metrics and writes a per-reviewer quality assessment plus a comparative verdict. This pass AUGMENTS the numbers — it never recomputes or overrides them.

Two layers of review-quality signal: