MDX-loader directory mapping fix
The marketing MDX loader was scanning singular directory names (feature/, doc/) while the actual content dirs were plural (features/, docs/) — every MDX-backed dynamic route silently 404ed in production. Added DIR_NAME map, mirrored in the embeddings indexer. All hand-written features + docs now render.
A pre-existing bug — the loader silently returned 0 pages because the singular type-key was used as the directory name. Discovered while running the embeddings indexer; verified `/features/memory` was 404ing in production. Fix unblocks 30+ MDX pages.
fixmdxseo404