Fixes #13381

Problem

When Controller is inside a React Native Activity (or any tab layout
that keeps components mounted but hidden), it shows a stale value when
the tab becomes visible again.

Steps to reproduce are in the issue with a CodeSandbox link:
https://codesandbox.io/p/sandbox/controller-activity-bug-6tpzdl

Why

useController uses useWatch internally. When a component is hidden
inside an Activity, React skips state updates to that subtree. So
useWatch misses the update and holds the old value.

Fix

control._formValues always has the latest value regardless of React's
render cycle. On each render, if _formValues and useWatch disagree,
we use _formValues instead. No extra re-renders.

Changes

• src/useController.ts — sync value from _formValues on render
• src/__tests__/useController.test.tsx — added regression test

Code of Conduct

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