Deleting worktree fails w/out recovery

When deleting a worktree as part of session delete it failed to delete because, I think, I had PS open to the worktree (Windows). Ideally it would force delete anyway but at least it should let me try again. I just showed this error.

Which stayed for a minute or something then disappeared.

I just saw it appear again so maybe there is some timer running to try again - I've closed consoles... maybe a detached web app or something is running.

====
Delete failed
Failed to delete session: The process cannot access the file because it is being used by another process. (os error 32)
======

It would be nice if the error mentioned what file / directory was being deleted. Maybe have a "try again" button or some info saying "this will be retried again every minute forever".

Start by reproducing session deletion on Windows while a PowerShell window is open in the worktree, then observe the displayed failure and whether it retries. Trace the session-delete worktree cleanup flow; done should provide a recoverable retry or clear retry behavior and identify the file or directory involved in the failure.

索引モデルが issue の本文から書いたものです。