fix(snapshots): Omit diff_mask_path for layout_changed images

odiff does not generate a mask file when images differ in dimensions,
so including a path would point to a non-existent file.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: NicoHinderling

src/commands/snapshots/diff.rs

@@ -224,12 +224,18 @@ pub fn execute(matches: &ArgMatches) -> Result<()> {
                             _ => "changed",
                         };
                         changed_count += 1;
+                        let mask = if status == "layout_changed" {
+                            let _ = fs::remove_file(&mask_path);
+                            None
+                        } else {
+                            Some(path_as_url(&mask_path))
+                        };
                         images.push(ImageResult {
                             name,
                             status: status.to_owned(),
                             diff_percentage: response.diff_percentage,
                             diff_pixel_count: response.diff_count,
-                            diff_mask_path: Some(path_as_url(&mask_path)),
+                            diff_mask_path: mask,
                             error: None,
                         });
                     }