v7.55.0

Paired engine: engine-service-v0.1.129 (REQUIRED_ENGINE_VERSION (0, 1, 129)),
unchanged from 7.54.0. No engine cut: pin and cloud are both at v0.1.129 with
no service/src/main drift.

Two epics land here. RDR-217 gives the client a lexical retrieval leg it never
had, and RDR-215 finishes retiring the bash hook layer.

Added

• nx search --lexical, and the lexical parameter on the MCP search
  tool (RDR-217). The engine has stored a full-text (tsvector) and a
  trigram index for every chunk since RDR-155 P3, and no client could read
  either: nx search was vector-only. --lexical ADDS exact-text hits to the
  vector results rather than replacing them.

  Measured on this repo's own code before the surface was designed: on
  rare-token queries, precision@10 goes from 0.167 to 0.698, and one query
  (word_similarity_threshold, present in two chunks) scored 0.000 precision
  AND 0.000 recall on the vector path — invisible to semantic search
  entirely. On identifier queries the vector path was already good (0.867) and
  the gain is small, so the honest claim is narrow: this helps where an exact,
  low-frequency token is what you have.

  It is ADDITIVE and cannot be a default, because the hybrid route gates on
  text before ranking: it returned zero rows for every prose query in the
  measurement. Selecting it instead of the vector leg would hand a
  natural-language question an empty result. Lexical hits are exempt from the
  per-collection distance threshold — a lexically-matched row whose vector
  distance is large is exactly the row worth having — and the flag REFUSES on
  a backend without the route rather than silently returning vector-only rows.

  --hybrid is unrelated and unchanged: it re-ranks vector results by git
  frecency and never changes which rows come back. The docs now say so at
  every site that recommends either.

• HttpVectorClient.hybrid_search, the first caller in this repository of
  POST /v1/vectors/hybrid-search — an endpoint with a production consumer
  and, until now, no caller in the repo that builds it. That gap is what
  BUG-0148 shipped through, and closing it is an argument for RDR-217 that
  does not depend on retrieval getting better.

Changed

• The bash hook layer is retired (RDR-215). Plugin hooks are MCP tools and
  exec-form verbs; the twelve bash hook scripts and the shell launcher are
  deleted, and 25 of 25 hooks.json entries across both plugin tiers are
  re-declared. The expectations_* ledger moved from a sourced bash library
  into nexus.hooks.expectations, reachable as nx-hook verbs.

Fixed

• Test harness containers no longer register as fresh installs. Every
  throwaway install on a virgin HOME mints a new install_id and pings the
  anonymous install counter; 18 of them reached production across two release
  nights and tripled the active-install figure with this project's own
  testing. Every docker run under tests/e2e now forwards
  NX_NO_TELEMETRY=1 — -e is the only channel in, since a container does
  not inherit the host environment — and the lint that checks this, which
  previously named one hardcoded file, now scans them all.

• The retrieval drift gate ranked by raw distance after the topic boost
  moved into its own field, so it was blind to the ranking layer while passing
  inside its threshold band. Re-pinning reproduced the original baseline
  exactly, which is the evidence it measures the right quantity again.

• nx store list groups document listings by the catalog manifest rather than
  by chunk hash, so a document whose chunks share text is listed once.

• A stored note whose embedding model imposes no token window is split on
  write and rejoined on read (nexus-b2tld). Notes written before this change
  are unaffected and are not re-embedded.

• nx search reports an honest raw distance alongside the score that actually
  ordered the row, instead of folding the topic boost into the distance
  (nexus-la5pr). --hybrid's frecency blend is unchanged.

• The client-side ripgrep path is deleted and its orphaned line caches are
  reaped (nexus-06aei). It was off by default, effectively never ran, and its
  caches silently truncated.

• A generation install prunes a shim it no longer owns (nexus-3z8vb).

Removed

• The twelve bash hook scripts and the shell hook launcher (RDR-215). If you
  referenced conexus/hooks/scripts/*.sh directly, those paths are gone; the
  behaviour lives in nexus.hooks as nx-hook verbs and MCP tools.

• The client-side ripgrep search path (nexus-06aei), as above.