Create @refrakt-md/vite plugin — Level 1 static transform

Acceptance Criteria

• New package packages/vite/ with package.json, tsconfig.json, build config
• Plugin entry (src/index.ts) exports refrakt() function returning a Vite plugin
• Config accepts packages, theme, extensions, injectCSS, level, contentDir
• Per-file transform pipeline: Markdoc parse → rune schema transforms → serialize → identity transform → renderToHtml
• Each .md file emits a JS module exporting html, tree, frontmatter, seo, meta
• seo export includes jsonLd array and og object via extractSeo() from @refrakt-md/runes
• meta export includes runes (list of rune names used) and packages (list of package names)
• Community packages loaded via loadRunePackage() and merged via mergePackages()
• Runes requiring Level 2 (breadcrumb, nav, glossary auto-linking) render as static content with build warning
• Plugin sets ssr.noExternal for refrakt packages (same CORE_NO_EXTERNAL pattern as sveltekit)
• vite is a peer dependency (^5.0.0 || ^6.0.0)
• Package builds successfully in monorepo dependency order
• Basic integration test: transform a .md file with runes, verify module exports

Approach

1. Scaffold packages/vite/ — package.json, tsconfig extending root, tsup build config
2. Implement config parsing and validation in src/index.ts
3. Implement per-file transform in src/transform.ts — reuses Markdoc.parse(), rune schemas from @refrakt-md/runes, serialize() from @refrakt-md/transform (requires WORK-088), createTransform(), and renderToHtml()
4. Wire up Vite's transform hook to intercept configured extensions
5. Emit JS module string with named exports
6. Add resolveId/load hooks for virtual module support (used by WORK-095)

Dependencies

• Extract shared utilities from @refrakt-md/svelte to @refrakt-md/transform — serialize() must be available from @refrakt-md/transform

References

• Vite Plugin — Framework-Agnostic Rune Integration (Architecture, Configuration, Level 1 sections)
• packages/sveltekit/src/plugin.ts — existing Vite plugin to reference
• packages/transform/src/engine.ts — identity transform
• packages/transform/src/html.ts — renderToHtml()