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.rs

@@ -2512,7 +2512,9 @@ pub mod tests {
             cx.update(|cx| syntax_chunks(DisplayRow(0)..DisplayRow(5), &map, &theme, cx)),
             [
                 ("fn \n".to_string(), None),
-                ("oute\nr".to_string(), Some(Hsla::blue())),
+                ("oute".to_string(), Some(Hsla::blue())),
+                ("\n".to_string(), None),
+                ("r".to_string(), Some(Hsla::blue())),
                 ("() \n{}\n\n".to_string(), None),
             ]
         );
@@ -2535,8 +2537,11 @@ pub mod tests {
             [
                 ("out".to_string(), Some(Hsla::blue())),
                 ("⋯\n".to_string(), None),
-                ("  \nfn ".to_string(), Some(Hsla::red())),
-                ("i\n".to_string(), Some(Hsla::blue()))
+                ("  ".to_string(), Some(Hsla::red())),
+                ("\n".to_string(), None),
+                ("fn ".to_string(), Some(Hsla::red())),
+                ("i".to_string(), Some(Hsla::blue())),
+                ("\n".to_string(), None)
             ]
         );
     }

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()
             });
         }