Vite plugin — Level 2 cross-page pipeline

Implement the level: 'pipeline' mode that runs the full four-phase cross-page pipeline at build time, enabling breadcrumbs, nav, glossary auto-linking, and other entity-dependent features.

Acceptance Criteria

When level: 'pipeline' and contentDir are set, plugin scans all .md files in contentDir at buildStart
Full pipeline runs via runPipeline() from @refrakt-md/content: parse → register → aggregate → post-process
Entity registry is built (EntityRegistryImpl) and available to all pages
Output modules include enriched meta with entities and crossPageDeps arrays
Cross-page runes (breadcrumb, nav, glossary) render fully resolved content
Page hierarchy derived from file system relative to contentDir; frontmatter can override title/slug
Pipeline results cached in memory; individual transform calls read from cache
Dev mode: file changes re-parse changed file; if entities change, dependent files are re-processed
@refrakt-md/content is an optional peer dependency (only needed for Level 2)
Clear error message if level: 'pipeline' is set but @refrakt-md/content is not installed
Clear error message if level: 'pipeline' is set but contentDir is missing

Approach

Implement src/pipeline.ts — wraps runPipeline() with Vite build lifecycle hooks
In buildStart: scan contentDir, run full pipeline, cache results
In transform: read from cache instead of re-processing
In dev mode: use handleHotUpdate to detect entity changes and selectively re-run pipeline phases
Reference packages/sveltekit/src/plugin.ts for existing buildStart pipeline pattern

Dependencies

WORK-094 — core plugin must exist first
WORK-096 — HMR infrastructure for dev mode re-processing

References

SPEC-031 (Level 2: Cross-Page Pipeline section)
packages/content/src/pipeline.ts — runPipeline() orchestrator
packages/content/src/registry.ts — EntityRegistryImpl