docs: improve React adapter package docs

[aose-yuu]

Purpose

Make the React adapter package easier to scan for first-time readers.

Summary

• Starts the README with a small counter molecule before introducing props, deep signals, and controlled values.
• Separates static props from live props getter usage and calls out the React dependency list requirement.
• Moves the controller molecule dialog example into a dedicated controlled values section.
• Adds the exported useSnapshot hook to the API reference.
• Updates the npm package description to mention React hooks, molecules, and signals directly.

Verification

• pnpm -s cicheck