agent_ui: Restore `Ctrl + >` behavior for whole lines (#54698)

Restores current line fallback when using `Ctrl + >` to add context to
the agent.

Release Notes:

- N/A
4f54a04147Neel committed on 5/7/2026, 12:40:53 PM· committed by GitHubparent9a125a5
6 files changedLine totals unavailable