Server-side JSON API endpoints that power the React islands. Five routes: docs-tree (returns hierarchical tree of docs-prefixed entries), preview (returns lightweight document metadata for hover popovers), search (stubbed — will use CF AI Search), graph (stubbed — returns empty graph), and backlinks (stubbed — returns empty array). Only docs-tree and preview are fully implemented; the other three are placeholder endpoints that return valid empty responses so client components degrade gracefully.
All endpoints export a GET: APIRoute handler following Astro’s API route convention. Responses are always JSON with explicit Content-Type headers. Implemented endpoints use getLiveCollection / getLiveEntry from astro:content to access R2 data through the live collection, then adapt results using fromCollectionEntry(). Stubbed endpoints return structurally valid empty payloads ({ items: [], total: 0 }, [], { nodes: [], links: [] }) so consumers never need to handle missing endpoints.
docs-tree: calls getLiveCollection("knowledge"), adapts all entries via fromCollectionEntry(), filters to path.startsWith("docs/"), derives slug from path, then passes through buildTree() to produce nested TreeNode[]. preview: reads type and id query params, calls getLiveEntry("knowledge", "content/{type}/{id}.json"), adapts the entry, and returns a trimmed payload (title, description, type, first 5 tags). search: reads q param but currently returns empty results. All responses are wrapped in try/catch with fallback empty payloads.
Consumed by React islands: DocsTreeNav fetches /api/docs-tree, PopoverPreview fetches /api/preview, SearchBar fetches /api/search, GraphView would fetch /api/graph. Depends on astro:content (getLiveCollection, getLiveEntry), @/lib/types (fromCollectionEntry), and @/lib/docs-tree (buildTree). Runs as SSR on Cloudflare Workers — each request hits R2 through the live collection loader.