Add integration_test case: scroll clips overflowing content

[beaucollins]

Adds an apps/integration_test case that documents a web-renderer regression on this branch (#148): a <scroll> with a fixed height renders at its content height instead of clipping/scrolling, so it overflows its bounds and pushes following siblings off-canvas.

Root cause

src/valdi_modules/src/valdi/web_renderer/src/elements/ScrollElementClass.ts — the scroll box's own height + overflow aren't applied to constrain it, so it grows to content.

Repro

Case scroll-overflow-clipping renders a height=200 scroll over 600px of content plus a sentinel below it. Web: the scroll box renders ~600px and the sentinel is shoved down/off. Native: the scroll is 200px and content scrolls within it. The web-vs-native diff fails.

Suggested fix

Apply the scroll element's own height + overflow so content is clipped/scrollable within the box.

[github-actions]

📊 PR Size: size/S

Total changes: 25 lines (1 files)

Top files changed:

• apps/integration_test/src/valdi/integration_test_app/src/IntegrationTestCases.tsx: +25 -0

_{Size calculated as additions + deletions. Labels: XS (<10), S (<50), M (<250), L (<1000), XL (1000+)}