Fix snapping issues

Author: alex-rawlings-yyc

src/__tests__/components/Interlinearizer.test.tsx

@@ -838,6 +838,45 @@ describe('Interlinearizer', () => {
     expect(screen.queryByText('Chapter 2')).not.toBeInTheDocument();
   });
 
+  it('tags each inline chapter header with its chapter number for snap targeting', () => {
+    renderInterlinearizer({
+      book: GEN_TWO_CHAPTER_BOOK,
+      scrRef: { book: 'GEN', chapterNum: 1, verseNum: 1 },
+      continuousScroll: false,
+    });
+
+    expect(screen.getByText('Chapter 1')).toHaveAttribute('data-chapter-start', '1');
+    expect(screen.getByText('Chapter 2')).toHaveAttribute('data-chapter-start', '2');
+  });
+
+  it('highlights the first verse of a chapter when the reference names verse 0 (the heading)', () => {
+    renderInterlinearizer({
+      book: GEN_TWO_CHAPTER_BOOK,
+      scrRef: { book: 'GEN', chapterNum: 2, verseNum: 0 },
+      continuousScroll: false,
+    });
+
+    // Verse 0 names the chapter heading, which is not a verse; the active-verse marker still lands
+    // on the chapter's first segment so a verse stays highlighted.
+    const activeIds = new Set(
+      capturedSegmentViewPropsList.filter((p) => p.isActive).map((p) => p.segment.id),
+    );
+    expect([...activeIds]).toEqual(['GEN 2:1']);
+  });
+
+  it('scrolls the chapter heading to the top when the reference names verse 0', () => {
+    const scrollSpy = jest.spyOn(Element.prototype, 'scrollIntoView');
+    renderInterlinearizer({
+      book: GEN_TWO_CHAPTER_BOOK,
+      scrRef: { book: 'GEN', chapterNum: 2, verseNum: 0 },
+      continuousScroll: false,
+    });
+
+    // The snap targets the chapter-2 heading element rather than the active verse-1 segment.
+    const heading = screen.getByText('Chapter 2');
+    expect(scrollSpy.mock.contexts).toContain(heading);
+  });
+
   it('renders the snap-to-active-verse button when segments are present', () => {
     renderInterlinearizer({ book: GEN_1_MULTI_BOOK });