fix(orchestrator): name kvb-git-gc for worktree-held branches

The pkgmgr wrappers replay renamed kvb-git-branch-gc: branch cleanup outside worktrees is now kvb-git-branch-cleanup, and removing merged branches with their worktrees is kvb-git-gc. The hub's held-by-worktree hint, the cleanup dialog and its test now name kvb-git-gc.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_hub_cleanup.py

@@ -117,7 +117,7 @@ class TestHubCleanup(HubCase):
     def test_a_branch_held_by_a_worktree_offers_no_delete_and_names_branch_gc(self):
         item = self.ready(True, True)
         done = self.branches()["feature/done"]
-        held = f"held by worktree {item['worktree']}: pkgmgr branch cleanup skips it, use branch gc (kvb-git-branch-gc, pkgmgr gc)"
+        held = f"held by worktree {item['worktree']}: pkgmgr branch cleanup skips it, use branch gc (kvb-git-gc, pkgmgr gc)"
         self.assertEqual((done["cleanup"], done["held"], done["plan"][1]), (None, held, held))
         status, body = self.sign([item])
         self.assertEqual((status, body.decode()), (400, f"feature/done in {item['repository']} is no merged-clean branch without skip reason at that tip in the tree file\n"))