When polecats run 'gt done' without --cleanup-status, the witness may
prematurely nuke the worktree before the refinery can merge.
This fix auto-detects git state:
- uncommitted: has uncommitted changes
- stash: has stashed changes
- unpushed: branch not pushed or has unpushed commits
- clean: everything pushed
Uses BranchPushedToRemote() which properly handles polecat branches
that don't have upstream tracking (compares against origin/main).
On error, defaults to 'unpushed' to prevent accidental data loss.
Fixes: #342
Co-authored-by: mayor <mayor@gastown.local>
91641b01a0