Prepopulate empty patch in example capture (#46480)

This makes it a smoother workflow to capture an edit prediction example
from Zed and then write what you'd expect the patch to be.

Release Notes:

- N/A
0afe91ff24Max Brunsfeld committed on 1/9/2026, 9:58:07 PM· committed by GitHubparentbf87d0e
3 files changedLine totals unavailable