{{pr-review}}

Use `changes_load` first to get the branch summary, changed file list, and commit list.
Interpret $ARGUMENTS as an optional base branch.
When no base or head is provided, a dirty worktree should return only uncommitted local changes; otherwise it should return the committed branch delta.
Do not publish PR comments.
Return a chat review with:
- an overall grade formatted like `★★☆☆☆`
- a short verdict on merge risk
- a concise list of high-confidence findings ordered by impact
- explicit mention when no material issues were found
- concise wording and only findings you are sure about
