Orchestration hygiene

Run pan hygiene when the operator wants one end-to-end audit of local commits,
the worktree, pull requests, agent/tmux consistency, merged branches, stale
workspaces, and disk headroom. Findings are reported without mutation.

Use pan hygiene --json for automation and pan hygiene --strict when findings
should fail a gate. pan hygiene --fix-safe may delete only branches confirmed
merged by GitHub; under disk pressure it may remove only terminal worktrees that
have no branch, open PR, live session, or uncommitted work. Adjust that cleanup
floor with pan hygiene --fix-safe --fix-disk-pressure-floor 25.

Never substitute stash, force-delete, reset, or force-push cleanup. If safe
cleanup reports no eligible candidates, surface the findings to the operator.