Fix dynamic select storybook test failure

- Modified `useOnFormValueChange` hook to correctly track `prevValue` using `useRef`.
- Updated `AutoCalculation` story to use `waitFor` instead of `setTimeout` to prevent CI race conditions.
- Updated `selectRadixOption` test helper to blur the trigger after selection (click on body) to simulate "clicking off" and ensure onBlur events fire.

Author: google-labs-jules[bot]

apps/docs/src/remix-hook-form/use-on-form-value-change.stories.tsx

@@ -347,17 +347,15 @@ export const AutoCalculation: Story = {
     await userEvent.type(quantityInput, '2');
 
     // Total should update to 200.00
-    await new Promise((resolve) => setTimeout(resolve, 100));
-    expect(totalInput).toHaveValue('200.00');
+    await waitFor(() => expect(totalInput).toHaveValue('200.00'));
 
     // Add discount
     const discountInput = canvas.getByLabelText(/discount/i);
     await userEvent.clear(discountInput);
     await userEvent.type(discountInput, '10');
 
     // Total should update to 180.00 (200 - 10%)
-    await new Promise((resolve) => setTimeout(resolve, 100));
-    expect(totalInput).toHaveValue('180.00');
+    await waitFor(() => expect(totalInput).toHaveValue('180.00'));
 
     // Submit form
     const submitButton = canvas.getByRole('button', { name: /submit order/i });