refactor(docs): use kumo components directly for instant reload

[invisal]

Summary

This PR refactors the kumo-docs-astro package to import Kumo components directly from source files instead of the built distribution, enabling instant hot module reloading during development.

Key Changes:

• Direct source imports: Updated Vite configuration to alias @cloudflare/kumo to ../kumo/src/index.ts instead of the built package
• Component registry loading: Switched from importing the packaged JSON to dynamically reading the registry file using readFileSync
• Tailwind CSS source scanning: Updated source directive to scan ../kumo/src/**/*.{js,jsx,ts,tsx} instead of dist/
• Style imports: Changed CSS import to point directly to source (../kumo/src/styles/kumo.css)
• TypeScript configuration: Added path mapping for @cloudflare/kumo to resolve to source files
• Dev server configuration: Added filesystem access permissions for the sibling kumo package

Benefits:

• ⚡ Instant reload: Changes to Kumo components now hot-reload immediately in the docs site without rebuilding the package
• 🔄 Better DX: Eliminates the need to run pnpm build in the kumo package during development
• 🛠️ Faster iteration: Component development is significantly faster with instant feedback