fix(navigation-menu): pass data-state to ViewportContentMounter

[LongTangGithub]

Closes #3786

Description

NavigationMenuContent has two rendering paths depending on whether a
NavigationMenuViewport is present:

• Without viewport — renders NavigationMenuContentImpl directly,
  with data-state passed explicitly. ✅
• With viewport — hands off to ViewportContentMounter, which stores
  props in a shared Map that the viewport renders from. data-state was
  never included in this handoff. ❌

This meant that when using forceMount with a NavigationMenuViewport,
the rendered content elements had no data-state attribute at all, making it
impossible to target open/closed states in CSS or animations.

Fix

Extract openState from getOpenState(open) into a shared variable and
pass it as data-state to ViewportContentMounter, mirroring what was
already done for the non-viewport path.

Manual Testing

A new Storybook story ForceMountWithViewport has been added to reproduce
this scenario. To verify:

1. Run pnpm dev and open Components/NavigationMenu → ForceMountWithViewport
2. Hover over a trigger — the attribute should toggle between "open" and "closed" on the corresponding content element

Video Demo of Fix

data-attribute-fixmp4.mp4

[changeset-bot]

🦋 Changeset detected

Latest commit: 8c88571

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@radix-ui/react-navigation-menu	Major
radix-ui	Patch

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