feat(react-ui): add Storybook stories for the genui-lib Form component

[Shinyaigeek]

Summary

Form is a genui-lib (openui-lang) component with no standalone React counterpart, so it had no Storybook coverage: the existing stories under components/*/stories exercise the plain React components, and the lang layer's Form container — validation wiring, primary-button validation, the FormControl input union — was never rendered anywhere in Storybook.

This PR adds stories that render openui-lang programs through Renderer with openuiLibrary — the same path an LLM response takes — so the lang-layer behavior (positional args, validation, Action) is visible as-is.

• Default — a contact form matching the library's own prompt example (Input / Select / TextArea with required rules and a hint)
• ValidationErrors — a play function submits the empty form, showing the per-field "This field is required" hints produced by the primary-button validation path
• AllControlTypes — covers the full FormControl input union: DatePicker, Slider, CheckBoxGroup, RadioGroup

The stories live under a new GenUI/ Storybook section to keep lang-layer components separate from Components/, and to give future lang-only stories (e.g. Stack) a home.

Testing

• Both openui-lang programs parse cleanly against openuiLibrary.toJSONSchema() (no errors, unresolved refs, or orphans)
• tsc --noEmit reports no errors for the new file
• Verified all three stories render in Storybook, including the play-function validation errors

🤖 Generated with Claude Code