[TheGreatAxios]

Closes CL-9431

In uncontrolled mode the setter resolved functional updates against the value captured at render, so two batched setValue((p) => p + 1) calls both saw the same base and produced 1 instead of 2 (and useDismissablePopover's double toggle stayed open).

The setter now resolves against a ref that holds the latest uncontrolled value and is updated synchronously on every set, then passes the result to setUncontrolledValue and onChange. Controlled mode still resolves against the controlled value.

Why a ref, not a React updater: calling onChange inside an updater would fire it twice under StrictMode, which double-invokes updaters. Keeping the side effect in the setter fires onChange once per call.

Tests: two batched functional updates give 2 with onChange called with 1 then 2 (via renderHook); onChange fires once under StrictMode; two batched useDismissablePopover toggles end closed. No public API change.