…mpatibility

React Compiler skips any component calling useVirtualizer as a
known-incompatible API: the hook returns a stable instance whose
getVirtualItems()/getTotalSize() read mutable internal state during render,
so a memoizing compiler caches the first result keyed on the stable
instance and the list never updates (TanStack#736, TanStack#743). The skip keeps apps
correct but leaves every consuming component un-memoized (TanStack#1119).

useVirtualizerSnapshot (and useWindowVirtualizerSnapshot) return the
render-facing values as immutable snapshot data instead, via
useSyncExternalStore (official shim, preserving the React >=16.8 peer
range): virtualItems and totalSize change identity exactly when the
computed geometry changes, while the stable virtualizer instance rides
along for imperative APIs (measureElement, scrollToIndex, ...). Because the
compiler's skip is keyed on the imported property name, components
consuming the snapshot hooks compile - and memoize correctly - today.

- snapshot cache rebuilt lazily on onChange, with part-comparison so
  notifications that change nothing visible (isScrolling flips) publish
  the same reference and skip the re-render
- user onChange still chained; useFlushSync semantics preserved
- unit tests pin the identity contract (stable across unrelated
  re-renders, fresh on geometry change), StrictMode, and SSR via
  getServerSnapshot
- compiler-contract tests run babel-plugin-react-compiler in CI: snapshot
  consumers emit the _c() memo cache, useVirtualizer consumers stay
  skipped
- e2e: a compiled snapshot-hook page under the existing react-compiler
  build (TanStack#1187 infra) proving the TanStack#736 scenario now passes with the
  consumer compiled