fix: gate header/footer X normalization on horizontal anchor

normalizeFragmentsForRegion was rewriting column-relative X whenever the
vertical anchor was page-relative, conflating the two independent OOXML
axes. Switch the gate to the horizontal anchor (hRelativeFrom === 'page')
so column-relative X stays content-local and the painter applies the
physical page margin exactly once. Update tests to cover both axes
independently.

Author: luccascorrea

packages/layout-engine/layout-engine/src/normalize-header-footer-fragments.test.ts

@@ -107,7 +107,7 @@ describe('normalizeFragmentsForRegion (header/footer page-relative anchors)', ()
       expect(fragment.x).toBe(24);
     });
 
-    it('normalizes column-relative X using the physical page margin when Y is page-relative', () => {
+    it('does not normalize column-relative X when Y is page-relative', () => {
       const imgWidth = 830;
       const block: FlowBlock = {
         kind: 'image',
@@ -123,11 +123,12 @@ describe('normalizeFragmentsForRegion (header/footer page-relative anchors)', ()
         },
       };
       const fragment = makeAnchoredImageFragment('header-column-background', 0, 40, imgWidth);
+      fragment.x = -76;
       const pages = [{ number: 1, fragments: [fragment] }];
 
       normalizeFragmentsForRegion(pages, [block], [makeDummyMeasure()], 'header', fullConstraints);
 
-      expect(fragment.x).toBe(-4);
+      expect(fragment.x).toBe(-76);
       expect(fragment.y).toBe(8);
     });
   });
@@ -207,7 +208,7 @@ describe('normalizeFragmentsForRegion (header/footer page-relative anchors)', ()
       expect(fragment.y).toBe(PAGE_HEIGHT - 40 - FOOTER_BAND_ORIGIN);
     });
 
-    it('does not rewrite page-relative X when the vertical anchor is not page-relative', () => {
+    it('normalizes page-relative X when the vertical anchor is not page-relative', () => {
       const block: FlowBlock = {
         kind: 'image',
         id: 'footer-cross-axis',
@@ -226,7 +227,7 @@ describe('normalizeFragmentsForRegion (header/footer page-relative anchors)', ()
 
       normalizeFragmentsForRegion(pages, [block], [makeDummyMeasure()], 'footer', fullConstraints);
 
-      expect(fragment.x).toBe(24);
+      expect(fragment.x).toBe((816 - 120) / 2);
       expect(fragment.y).toBe(12);
     });
 

packages/layout-engine/layout-engine/src/normalize-header-footer-fragments.ts

@@ -72,6 +72,7 @@ function isAnchoredFragment(fragment: Fragment): boolean {
 }
 
 function isPageRelativeBlock(block: FlowBlock): block is ImageBlock | DrawingBlock {
+  // This is a union-of-axes gate; each normalization branch re-checks its own axis.
   return (
     (block.kind === 'image' || block.kind === 'drawing') &&
     (block.anchor?.hRelativeFrom === 'page' || block.anchor?.vRelativeFrom === 'page')
@@ -121,7 +122,9 @@ export function normalizeFragmentsForRegion(
       const block = blockById.get(fragment.blockId);
       if (!block || !isPageRelativeBlock(block)) continue;
 
-      if (pageWidth != null && block.anchor?.vRelativeFrom === 'page') {
+      // Horizontal and vertical anchors are independent in OOXML. Keep column-relative X
+      // content-local so the painter can add the physical page margin exactly once.
+      if (pageWidth != null && block.anchor?.hRelativeFrom === 'page') {
         const fragmentWidth = (fragment as { width?: number }).width ?? 0;
         const marginLeft = Math.max(0, constraints.margins.left ?? 0);
         const marginRight = Math.max(0, constraints.margins.right ?? 0);