agent_ui: Handle Cut for selection mentions (#54694)

Following on from https://github.com/zed-industries/zed/pull/54031,
implement the same but for `Cut`.

Release Notes:

- N/A
1b88528b86Neel committed on 5/7/2026, 6:07:12 PM· committed by GitHubparent8624bf6
2 files changedLine totals unavailable