debugger: Improve saving scenarios through new session modal (#30566)

- A loading icon is displayed while a scenario is being saved
- Saving a scenario doesn't take you to debug.json unless a user clicks
on the arrow icons that shows up after a successful save
- An error icon where show when a scenario fails to save
- Fixed a bug where scenario's failed to save when there was no .zed
directory in the user's worktree


Release Notes:

- N/A
8294981ab5Anthony Eid committed on 5/12/2025, 1:39:45 PM· committed by GitHubparenta3105c9
2 files changedLine totals unavailable