8 bump to react 19

[krowvin]

Add compatibility for react 18 and 19

• react and react-dom are peerDependencies with ^18.2.0 || ^19.0.0
• local dev tooling updated to a React 19 stack
• Vite and Vitest were upgraded so the repo builds and tests
• CI workflow added to validate React 18 / 19
• global store usage in the public hook / layer callback path changes
• linter