Rewrite a feature branch's commit history into clean conventional commits that tell a progressive, linear story. Handles backup, soft reset, and atomic recommit. Use when: (1) Cleaning up messy WIP commits before PR, (2) Reorganizing commits into logical units, (3) Converting commits to conventional commit format. Triggers on: "rewrite history", "clean up commits", "rewrite commits", "conventional commits", "squash and rewrite", "reorganize commits".