Lakebase Search: vector and BM25 on Neon

Today we're shipping the beta of Lakebase Search on Neon: hybrid vector + full-text retrieval via two Postgres extensions, lakebase_vector and lakebase_text. This post is the story of why and how we built it: IVF + RaBitQ instead of HNSW, BM25 with top-K pushdown instead of GIN on tsvector, and indexes that live on object storage so they survive scale-to-zero and branch instantly.