Worktree cleanup

Agent work creates one worktree per branch; they pile up. Never delete anything without showing the list and getting an explicit OK.

1. Collect

git fetch -q --prune origin
git worktree list --porcelain

For every worktree except the main checkout, determine:

• branch (or detached HEAD) and last commit date (git -C <path> log -1 --format=%cr),
• uncommitted changes: git -C <path> status --porcelain (count tracked + untracked),
• merged: git branch --merged origin/main contains the branch, or gh pr list --state merged --head <branch> finds a merged PR (squash merges don't show up as merged in git),
• open PR: gh pr list --state open --head <branch>,
• prunable: marked prunable by git (directory already gone).

2. Propose

Show a table grouped as:

1. Safe to remove — merged (or PR merged), no uncommitted changes.
2. Probably done — no open PR, last commit older than 30 days, no uncommitted changes.
3. Keep — open PR, uncommitted changes, or recent work. List why.

3. Remove (after OK, per group or per entry)

git worktree remove <path>          # refuses if there are uncommitted changes — good
git branch -d <branch>              # only for merged branches; -D only if the person says so
git worktree prune

Never use --force on a worktree with uncommitted changes unless the person explicitly asked for that specific one. Report what was removed and what was kept.