fix(pptx): background rendering - gradient inheritance and page fill reset

crates/office2pdf/src/render/typst_gen.rs

@@ -409,7 +409,7 @@ fn generate_fixed_page(
     } else {
         let _ = writeln!(
             out,
-            "#set page(width: {}pt, height: {}pt, margin: 0pt)",
+            "#set page(width: {}pt, height: {}pt, margin: 0pt, fill: white)",
             format_f64(size.width),
             format_f64(size.height),
         );

crates/office2pdf/src/render/typst_gen_fixed_page_textbox_tests.rs

@@ -879,8 +879,8 @@ fn test_fixed_page_text_box_no_fill_no_stroke() {
     )]);
     let output = generate_typst(&doc).unwrap();
     assert!(
-        !output.source.contains("fill:"),
-        "Expected no fill in output, got:\n{}",
+        output.source.contains("fill: white"),
+        "Expected fill: white for no-background slide, got:\n{}",
         output.source,
     );
     assert!(

crates/office2pdf/src/render/typst_gen_page_misc_tests.rs

@@ -274,7 +274,11 @@ fn test_fixed_page_without_background_color() {
     });
     let doc = make_doc(vec![page]);
     let output = generate_typst(&doc).unwrap();
-    assert!(!output.source.contains("fill:"));
+    assert!(
+        output.source.contains("fill: white"),
+        "Expected fill: white for no-background slide, got:\n{}",
+        output.source
+    );
 }
 
 #[test]

crates/office2pdf/tests/pptx_fixtures.rs

@@ -128,7 +128,6 @@ fn smoke_pr_188_contributor_acceptance_fixtures() {
 }
 
 #[test]
-#[ignore = "pending PR #188 adaptation: reset a slide without a background to white"]
 fn acceptance_pr_188_contributor_acceptance_page_fill_reset() {
     let data = load_fixture(PR_188_PAGE_FILL_FIXTURE);
     let (document, _warnings) = PptxParser