docs: improve Vue adapter package docs

[aose-yuu]

Purpose

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

Summary

• Starts the README with a small counter molecule before introducing props, writable signals, deep signals, and controlled values.
• Separates static props from live props getter usage and calls out Vue reactive tracking.
• Moves the controller molecule dialog example into a dedicated controlled values section.
• Adds the exported useSnapshot composable to the API reference.
• Updates the npm package description to mention Vue 3 composables, molecules, and signals directly.

Verification

• pnpm -s cicheck