fix: shadow DOM scroll events — addGlobalScrollListener utility + close-on-scroll fix

[pzaczkiewicz-athenahealth]

Summary

Fixes #10093. The `scroll` DOM event has `composed: false`, meaning it does not propagate out of shadow roots — not even in the capturing phase. This silently broke two behaviours when `enableShadowDOM()` is in use:

1. Virtualizer / ScrollView — `document.addEventListener('scroll', onScroll, true)` never fires for elements inside a shadow root, so the virtualizer never updates which items are visible during scroll.
2. `useCloseOnScroll` (overlays) — `window.addEventListener('scroll', onScroll, true)` never fires for scrollable ancestors inside a shadow root, so combobox/popover overlays do not close when their ancestor scrolls.

Approach

Added `addGlobalScrollListener` to `DOMFunctions.ts` — the established home for shadow-DOM-safe DOM wrappers. When `shadowDOM()` is off the function attaches only to the global target, identical to the original code. When `shadowDOM()` is on it additionally walks the ancestor chain from a reference element, collects every `ShadowRoot` found, and attaches a capturing `scroll` listener to each.

Updated all affected callers to use this utility:

• `packages/react-aria/src/virtualizer/ScrollView.tsx` (replaced manual shadow-root-walking code from an earlier partial fix)
• `packages/react-aria/src/overlays/useCloseOnScroll.ts`
• `packages/@adobe/react-spectrum/src/menu/useCloseOnScroll.ts`

Callers that attach scroll listeners directly to a local element (`TabPanelCarousel.tsx`, `Pagination.tsx`) and the `visualViewport` listener in `useOverlayPosition.ts` are unaffected — they don't rely on event propagation crossing shadow boundaries.

`vitest.browser.config.ts` has a new `define: { 'process.env.VIRT_ON': '1' }` entry required for the Tree browser test: without it, the virtualizer treats `NODE_ENV=test` as a signal to use `Infinity` for viewport dimensions and skips virtualization, making the scroll test meaningless.

Pull Request Checklist

• Identified root cause: `scroll` events are `composed: false` and do not propagate out of shadow roots, even in the capture phase on `document`/`window`
• Audited all `addEventListener('scroll'/'scrollend')` usages in library code; confirmed which rely on global propagation vs. direct element attachment
• Created `addGlobalScrollListener` in `DOMFunctions.ts`, gated on `shadowDOM()` flag — light-DOM behaviour is unchanged when the flag is off
• Updated `ScrollView.tsx` to use the new utility (removed manual ancestor-walking code)
• Updated both copies of `useCloseOnScroll.ts` to use the new utility
• Types compile cleanly (`yarn check-types:tsc`)
• New browser tests written, confirmed to fail before the fix and pass after (see Test Instructions)
• 296 existing unit tests pass across Tree, VirtualizedMenu, and all overlay suites (1 pre-existing skip)

Test Instructions

Automated browser tests (Chromium)

`packages/react-aria-components/test/Tree.browser.test.tsx` — Virtualizer / ScrollView:

yarn vitest --config vitest.browser.config.ts run packages/react-aria-components/test/Tree.browser.test.tsx --project=chromium-desktop

Mounts a 50-item virtualized Tree inside a shadow root, scrolls the treegrid, and asserts Item 0 leaves the DOM while Item 20 appears.

`packages/react-aria-components/test/Select.browser.test.tsx` — useCloseOnScroll:

yarn vitest --config vitest.browser.config.ts run packages/react-aria-components/test/Select.browser.test.tsx --project=chromium-desktop

• Light DOM test: Opens a ComboBox inside a scrollable div, fires a scroll event, confirms the popover closes — regression guard, passes before and after.
• Shadow DOM test: Same setup inside a shadow root — fails before the fix, passes after.

Existing unit tests

yarn jest packages/react-aria-components/test/Tree.test.tsx packages/react-aria-components/test/VirtualizedMenu.test.tsx
yarn jest packages/react-aria/test/overlays/

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