zeta2: Build edit prediction prompt and process model output in client (#41870)

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>
Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>

crates/editor/src/editor_tests.rs

@@ -22915,7 +22915,7 @@ async fn assert_highlighted_edits(
     let text_anchor_edits = edits
         .clone()
         .into_iter()
-        .map(|(range, edit)| (range.start.text_anchor..range.end.text_anchor, edit))
+        .map(|(range, edit)| (range.start.text_anchor..range.end.text_anchor, edit.into()))
         .collect::<Vec<_>>();
 
     let edit_preview = window