editor: Fix panic when full width crease is wrapped (#31960)

Closes #31919

Release Notes:

- Fixed a panic that could sometimes occur when the agent panel was too
narrow and contained context included via `@`.

---------

Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/editor/src/display_map/wrap_map.rs

@@ -933,7 +933,7 @@ impl<'a> Iterator for WrapChunks<'a> {
             self.transforms.next(&());
             return Some(Chunk {
                 text: &display_text[start_ix..end_ix],
-                ..self.input_chunk.clone()
+                ..Default::default()
             });
         }