work-with-pr

Full PR lifecycle: git worktree → implement → atomic commits → PR creation → verification loop (CI + review-work + Cubic approval) → merge. Keeps iterating until ALL gates pass and PR is merged. Worktree auto-cleanup after merge. Use whenever implementation work needs to land as a PR. Triggers: 'create a PR', 'implement and PR', 'work on this and make a PR', 'implement issue', 'land this as a PR', 'work-with-pr', 'PR workflow', 'implement end to end', even when user just says 'implement X' if th