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/codestral/src/codestral.rs

@@ -34,7 +34,7 @@ struct CurrentCompletion {
     snapshot: BufferSnapshot,
     /// The edits that should be applied to transform the original text into the predicted text.
     /// Each edit is a range in the buffer and the text to replace it with.
-    edits: Arc<[(Range<Anchor>, String)]>,
+    edits: Arc<[(Range<Anchor>, Arc<str>)]>,
     /// Preview of how the buffer will look after applying the edits.
     edit_preview: EditPreview,
 }
@@ -42,7 +42,7 @@ struct CurrentCompletion {
 impl CurrentCompletion {
     /// Attempts to adjust the edits based on changes made to the buffer since the completion was generated.
     /// Returns None if the user's edits conflict with the predicted edits.
-    fn interpolate(&self, new_snapshot: &BufferSnapshot) -> Option<Vec<(Range<Anchor>, String)>> {
+    fn interpolate(&self, new_snapshot: &BufferSnapshot) -> Option<Vec<(Range<Anchor>, Arc<str>)>> {
         edit_prediction::interpolate_edits(&self.snapshot, new_snapshot, &self.edits)
     }
 }
@@ -281,8 +281,8 @@ impl EditPredictionProvider for CodestralCompletionProvider {
                 return Ok(());
             }
 
-            let edits: Arc<[(Range<Anchor>, String)]> =
-                vec![(cursor_position..cursor_position, completion_text)].into();
+            let edits: Arc<[(Range<Anchor>, Arc<str>)]> =
+                vec![(cursor_position..cursor_position, completion_text.into())].into();
             let edit_preview = buffer
                 .read_with(cx, |buffer, cx| buffer.preview_edits(edits.clone(), cx))?
                 .await;