agent_ui: Fix text pasting no longer working (#42914)

Regressed in https://github.com/zed-industries/zed/pull/42908
Release Notes:

- N/A *or* Added/Fixed/Improved ...
3f25d36b3cLukas Wirth committed on 11/17/2025, 9:04:50 PM· committed by GitHubparentf015368
1 file changedLine totals unavailable