Smoke tests

[skrulling]

This PR introduces smoke tests for both @highcharts/grid-lite-react and @highcharts/grid-pro-react. It refactors the shared test utilities to support dynamic option updates and significantly improves the robustness of the useGrid hook to handle initialization race conditions.

Changes

Testing

• New Smoke Tests: Added Grid.test.tsx for both Lite and Pro packages to verify basic rendering, ref access, and callbacks.
• E2E Tests: Added tests that serve the React and Next.js demos and make sure that they a functional.

Core Logic

• useGrid Hook: Improved robustness in packages/grid-shared-react/src/hooks/useGrid.ts:
  • Added initStartedRef to prevent double initialization.
  • Implemented pendingOptionsRef to queue option updates that occur while the grid is asynchronously initializing.
  • Added cleanup checks to prevent errors if the component unmounts during initialization.

Verification

• Run pnpm test:all to verify all smoke tests pass without warnings.
• Run pnpm build to ensure TypeScript compilation succeeds across all packages.

[ddragula]

Nice!

[sebastianbochan]

I'm unable to run NextJS demos; the screen is blank.