* docs(adr): add ADR-160 for ACORN predicate-agnostic filtered HNSW
Records the decision to ship ruvector-acorn as the ruvector solution for
filtered vector search recall collapse at low predicate selectivity. Documents
3 concrete index variants, measured benchmark results, consequences, and a
4-phase implementation roadmap (NN-descent, payload index, delta-index, SIMD).
https://claude.ai/code/session_0173QrGBttNDWcVXXh4P17if
* docs(research): add nightly research doc — ACORN filtered HNSW (2026-04-26)
Full research document: SOTA survey (SIGMOD 2024, competitor changelog),
proposed design with graph construction + ACORN beam search pseudocode,
implementation notes (greedy vs NN-descent, entry point selection, predicate
generality), real benchmark methodology and results table, blog-readable
walkthrough, failure modes, roadmap, and production crate layout proposal.
https://claude.ai/code/session_0173QrGBttNDWcVXXh4P17if
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Co-authored-by: Claude <noreply@anthropic.com>
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