modernize

Modernize starts with guardrails: pull the latest origin for the working branch, the main branch and any related branch before starting; treat existing worktree changes as user-owned, using a disposable worktree when the active worktree is dirty or in use elsewhere; and remember that modernizing authorizes rebasing and updating the PR branch only. It does not authorize merging, closing, changing the base branch, or expanding scope. It never uses an unqualified force push: a rebased branch is updated with force-with-lease against the head SHA observed before the rebase. It posts no PR comment unless the user asked for one. The PR's intent is established first: URL, state, base, head repository and branch, current head SHA, author, checks and review state, plus title, body, linked issues, commits, review threads and complete diff. The smallest coherent goal the PR was trying to accomplish is stated before its implementation is judged. Then the base branch is inspected for commits and diffs added since the PR diverged, including merged and open PRs that suggest a replacement or a competing implementation. The check looks beyond overlapping lines: has the same user-facing problem already been solved, did APIs, types, schemas, dependencies or architectural boundaries change, do both sides now claim the same behavior, was the code deleted, moved or intentionally simplified, would landing the PR restore an old behavior or create two ways to do the same thing, and is the original benefit still large enough to justify the maintenance cost? The disposition is chosen before pushing. MODERNIZE means the goal is still useful and the implementation remains the right shape: rebase, resolve conflicts, test and update the branch. REWORK means the goal is still useful but a mechanical rebase would preserve the wrong implementation: explain the smallest credible rewrite and stop before pushing unless the user also asked for that rework. CLOSE means the PR is superseded, obsolete, directionally wrong, or no longer worth its cost: cite concrete evidence and stop, without spending time rebasing an obsolete branch. For a MODERNIZE disposition, the rebase uses a safe local branch or disposable worktree, resolves each conflict according to the PR's current intent and the base branch's newer invariants, compares the pre-rebase and post-rebase series with git range-diff, runs the repository's focused checks for the touched area, and pushes with force-with-lease. If the lease fails, fetch and reassess rather than overwriting new work. Limits as written in the SKILL.md: do not merge the PR, and do not close it without explicit permission. Do not describe a PR as current merely because Git reports no conflicts. Separate observed facts from judgment, and say what could not be verified instead of manufacturing confidence. The report leads with MODERNIZE, REWORK or CLOSE and the reason, then summarizes base branch changes, conceptual conflicts or their absence, the rebase and push result if performed, checks run and their results, and the remaining decision or work, with a link to the PR.