Description

Closes #13206

This PR fixes a bug where the subscription callback triggers twice when a field is both watched (via useWatch or watch) and subscribed to.

Problem

In the setValue function within createFormControl.ts, the state update notification (_subjects.state.next) was being triggered twice under specific conditions:

1. First, inside the if (isWatched(name, _names)) block.
2. Second, unconditionally at the end of the function.

This caused subscribers to receive duplicate events for a single value change.

Solution

I refactored the notification logic in setValue to use an if/else block. Now, _subjects.state.next is guaranteed to be called exactly once:

• If Watched: Sends the update including the full form state and values.
• If Not Watched: Sends the standard update logic.

Testing

I have added a reproduction test case in src/__tests__/issue-13206.test.tsx.
This test spies on control._subjects.state.next to verify that it is invoked exactly once when setValue is called on a watched field.

// Key verification logic in the test
expect(nextSpy).toHaveBeenCalledTimes(1);