Reranker as the precision stage + fold glossing into Build Index (#85)

Codebase quality pass: kill silent-truncation hacks, fix latent bugs, cover them (#46)

Switch embeddings to a local CPU model (bge-small): free tier APIs can't index the corpus

Build Index: fail fast on missing secrets, stream progress unbuffered

M2 indexing: Neon schema, resumable Gemini embedding, one-command build script