Properly handle goto single file worktrees during terminal cmd-clicks (#26582)

Closes https://github.com/zed-industries/zed/issues/26431
Follow-up of https://github.com/zed-industries/zed/pull/26174

`path_with_position.path.strip_prefix(&worktree_root)` used in the PR is
wrong for cases of single-file worktrees, where it will return empty
paths that will result in incorrect project and FS entries accessed.

Release Notes:

- Fixed goto single file worktrees during terminal cmd-clicks