Handle drag and drop in new agent threads (#35879)

This is a bit simpler than for the original agent thread view, since we
don't have to deal with opening buffers or a context store.

Release Notes:

- N/A
f3a58b50c4Cole Miller committed on 8/8/2025, 7:03:50 PM· committed by GitHubparent2cde6da
3 files changedLine totals unavailable