Add shadcn coverage and fix overlay, layout, and selector regressions

[jwxbond]

Summary

• add and refresh shadcn integration coverage and snapshots
• fix listview overlay stacking, RTL/grid, textarea, and selector regressions found during integration testing
• add hover fallback handling for the :focus-within + :hover integration path and update its snapshots

Testing

• flutter test test/src/rendering/css_selectors_interactive_pseudo_test.dart --plain-name "document hover targeting falls back to nearest ancestor with target-side :hover selectors"
• cd integration_tests && WEBF_TEST_NAME_FILTER=':focus-within combined with :hover' LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 npm run integration -- --skip-build specs/css/css-selectors/pseudo-focus-within.ts
• targeted integration runs for listview, shadcn popover, and RTL/grid regressions during the branch work

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Project	Deployment	Actions	Updated (UTC)
use-case	Ready	Preview, Comment	Apr 12, 2026 2:11am
vue_usecase	Ready	Preview, Comment	Apr 12, 2026 2:11am

[andycall]

This impls make the list view to be a single child scroll view