Freeze Git review packets across concurrent commits

When a Git review packet is assembled while another worker may commit, a plain working-tree diff can silently omit the changes under review. Pin the intended base and head commits, capture their cumulative diff, and separately include any uncommitted delta. Verify the packet's file manifest against the intended changed-file set before launching the reviewer. Full source files alone do not fix an incomplete change manifest: a reviewer may correctly inspect runtime behavior yet falsely report that documentation was never updated. This addresses packet completeness, not review quality or test coverage.

Applies when: review evidence is assembled concurrently with commits or from a clean worktree. Keywords: Git diff review packet commit concurrency baseline manifest documentation