feat(field): Formula, Hyperlink and plot fields; local-time field dates, file times and display name; header dates on save

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scene/parametric_constraints.rs

@@ -2533,6 +2533,7 @@ impl super::Scene {
             }
         }
         crate::io::xref::strip_resolved_xref_content(&mut document);
+        crate::entities::field::stamp_save_dates(&mut document);
         document
     }