Package install

Use the package-install language with either package names or one npm command:

```package-install
foldocs foldkit effect
```

Foldocs compiles the source into npm, pnpm, Yarn, and Bun commands. The UI keeps the selected manager synchronized across every install block and remembers the choice in the browser.

Development dependencies

An npm command retains flags while being converted:

```package-install
npm install --save-dev @foldocs/vite
```

The source Markdown route preserves the authored fence rather than serializing four generated variants.