Summary

Three related fixes to form-sheet stacking on web.

• Clip parent to form-card box when a form-sheet child opens, so the parent doesn't peek above/around the centered card. Geometry is read from the child's inline styles (not getBoundingClientRect) to get the at-rest box, unskewed by vaul's slide-in. clip-path animates with the same duration/easing as the cascade transform so the visible box and the drawer content slide together.
• Skip cascade transform when a form-sheet parent has a page-sheet child — mirrors iOS, where the page covers the form entirely. Avoids the parent peeking above the page mid-animation.
• Cascade tracks only the immediate child's snap point. Previously walked all descendants and pushed the parent further when a grandchild opened — even when the immediate child stayed put (e.g., child skipped its cascade for a page grandchild), leaving a visible gap.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Test Plan

• Open form sheet → open form-sheet child: parent clips to child's box, no peek above.
• Open form sheet → open page-sheet child: parent stays put, no cascade.
• Open form sheet (main) → open form-sheet child (basic) → open page-sheet grandchild: main does not shift further when grandchild opens; basic skips cascade for page grandchild.
• Dismiss children: clip releases, parent returns to original position.

Checklist

• I tested on iOS
• I tested on Android
• I tested on Web
• I updated the documentation (if needed)
• I added a changelog entry (if needed)