workspace::Open: Fix trapped cursor/selection on update (#25402)

Closes #ISSUE

Issue: Selection index does not reset when the matches update, which can
lead to the selection getting trapped when that index does not exist in
the next matches.


https://github.com/user-attachments/assets/d3fab23f-750c-47fb-bd3b-a0c42f214c83

This is in workspace::Open with   "use_system_path_prompts": false

Release Notes:

- N/A

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/file_finder/src/open_path_prompt.rs

@@ -266,6 +266,7 @@ impl PickerDelegate for OpenPathDelegate {
                         *m,
                     )
                 });
+                this.delegate.selected_index = 0;
                 cx.notify();
             })
             .ok();