Auto-cleaned worktree does not clean up corresponding branch

[SunYanbox]

Description

When the auto-cleanup feature removes a worktree, the corresponding Git branch is not automatically deleted.

Steps to Reproduce

1. Create a worktree (which creates a corresponding branch)
2. Use the auto-cleanup feature to remove the worktree
3. Check the local branch list

Expected Behavior

When a worktree is cleaned up, its corresponding local branch should also be deleted automatically.

Actual Behavior

The worktree is removed, but the corresponding local branch remains.

Suggestion

When cleaning up a worktree, if the corresponding branch is not being used by any other worktree, it should be automatically deleted.