commit-fixup

Absorb uncommitted changes into the existing commit each one should have been part of, leaving clean history. Four stages: safety checks → mapping → scope confirmation → execution and verification. This rewrites history, so don't skip any stage's checks.

1. Safety checks

git status --short                       # uncommitted changes
git merge-base HEAD origin/<default-branch>  # establish base (use the repo's default branch)
git log --oneline <base>..HEAD           # commits in scope
git branch -vv                           # upstream and push state
git log --merges --oneline <base>..HEAD  # merge commits in range
git --version

Tell the user before proceeding if any of these hit: