PDF: give the test-only Graphic literals the layer_options field

Graphic gained an optional layer_options field, so the test-only literals in the PDF
crate and in the engine's optional-content support need it. No behaviour changes.

crates/engine/tests/support/optional_content.rs

@@ -115,6 +115,7 @@ pub fn document(bytes: Vec<u8>, hidden_sets: &[&[&str]]) -> Document {
             crop: [0.0; 4],
             wrap: Default::default(),
             fill: Default::default(),
+            layer_options: None,
         });
         doc.insert_item(SpreadRef::Doc(0), item, None).unwrap();
     }

crates/pdf/src/export.rs

@@ -2009,6 +2009,7 @@ mod image_content_cache_tests {
                 crop: [0.0; 4],
                 wrap: Default::default(),
                 fill: Default::default(),
+                layer_options: None,
             };
             ex.graphic_unclipped(&mut surface, &graphic, hidden.as_deref());
             assert!(ex.layer_error.is_none());

crates/pdf/src/registration_tests.rs

@@ -17,6 +17,7 @@ fn placed_document(source: Vec<u8>) -> Document {
         crop: [0.0; 4],
         wrap: Default::default(),
         fill: Default::default(),
+        layer_options: None,
     });
     doc.insert_item(SpreadRef::Doc(0), item, None).unwrap();
     doc