Task 560: Add E2E tests for inline 3D viewer in cross-episode report

Status: DONE

Added 9 E2E tests verifying the inline 3d-viewer: directive renders correctly

in the cross-episode report page. Previously only the standalone orbital-3d.html

had E2E coverage.

1. viewer3d figure element exists

2. viewer3d container has correct data-scene/data-scenes attributes

3. 3 scene switcher buttons with correct Japanese labels

4. first scene button is active by default

5. timeline controls (play, slider, time) attached

6. play button aria-label

7. slider aria-label and range

8. view mode toggle button with aria-label and text

9. drag/zoom hint and caption text