Per-repo semantic search index: chunks a repo (via Beamscope.Chunking.Pipeline), embeds each chunk (via Beamscope.Embeddings), and persists {key, vector, metadata} rows to a DETS table at <repo_path>/.beamscope/search.dets — a build artifact of the target repo, parallel to _build/, meant to be gitignored there.

DETS is the durable store; like Beamscope.Callgraph.Store, the built index also lives in this GenServer's in-memory state as a plain list, so repeated searches are in-memory scans rather than repeated disk reads. DETS exists so a server restart doesn't require re-embedding an entire repo — get_or_build/2 opens an existing table if one is already on disk instead of rebuilding from scratch.

A fresh build writes to a search.dets.tmp.<unique> file, only renamed to the real search.dets path after a clean :dets.close/1 — so a process crash mid-build (e.g. kill -9) leaves only the temp file behind rather than leaving the real file "not properly closed" (which triggers DETS's automatic repair-on-reopen, and can reset it to empty).

Search is brute-force cosine similarity over the in-memory vector list. Realistic scale here is tens of thousands of vectors per repo, well within what a linear scan handles in well under a second — no ANN index needed.

Returns {:error, :embeddings_not_available} from any operation that needs to embed text if the optional bumblebee/nx/torchx deps (see Beamscope.Embeddings) aren't installed.