docs: search plan + counters for v1.2.0; tools/search-parity (parity + latency vs a brute-force reference)

README.md

@@ -22,7 +22,7 @@ in the Go binary (no database port at all) — all metadata I/O is mediated by t
 | **DB-file mutex** | Bash `flock` loop in `docker/leader-election.sh` only `exec`s supervisord on the winner, so two containers sharing one `/meta-core` volume can never run two writers on the database file. It is a mutex, not discovery — nothing reads the lock. |
 | **Embedded SQLite store** | One schema-free `kv(k, v)` table in `/meta-core/db/meta-core.db` (pure-Go `modernc.org/sqlite`, WAL, `synchronous=NORMAL`). One writer goroutine with group commit; a record write (fields + root index + CID aliases + FTS row + events) is atomic. Replaced Redis in 2026-10 (Redis + the in-memory search copy needed ~6.6 GB on watch.nsl.sh's 169k records; the SQLite file is ~2.5 GB on disk with a bounded page cache). |
 | **HTTP API** | Typed REST surface (gorilla/mux) for metadata, KV browsing, snapshots, schema inference, mounts, watchers, neighbours, identity, UDL, and file access by CID. |
-| **Indexed search** | `POST /api/metadata/search` builds a superset of candidates in SQL — a partial expression index `kv_field` over (field name, value) of every record key, plus an FTS5 trigram table — then verifies each with the unchanged Go matchers. Fresh immediately, no in-memory copy (`internal/storage/search.go`, `internal/api/search_index.go`). |
+| **Indexed search** | `POST /api/metadata/search` builds a superset of candidates in SQL — a partial expression index `kv_field_v` over (field name, value) of every record key, plus an FTS5 trigram table; the smallest part drives, the other filters are probed per candidate — then verifies each with the unchanged Go matchers. Fresh immediately, no in-memory copy (`internal/storage/search.go`, `internal/api/search_index.go`). |
 | **SSE event streams** | `/api/events/files` and `/api/events/meta` mirror the store's `file:events` / `meta:events` streams so external services never touch the store. `meta:events` entries are written in the same transaction as the change. |
 | **WebDAV server** | `/webdav/*` exposes the `/files` volume (read+write) for cross-service file access. nginx in front of meta-core handles caching. |
 | **Service discovery** | beacon v2: UDP multicast advertise/listen on `239.255.99.1:9099`, neighbours served at `/neighbors`. The file-based registry under `/meta-core/services/*.json` it replaced is gone. |
@@ -425,7 +425,7 @@ the repo-root [`METADATA_KEYS.md`](../../METADATA_KEYS.md).
 | `internal/leader` | `LeaderInfoProvider` — builds the `/urls` payload from hostname/IP/config; no election logic. |
 | `internal/meshdisco` | beacon v2 node (advertise, probe, neighbour map) — the Go port of the spec. |
 | `internal/kv` | Storage engine: SQLite `kv` table, single writer + group commit, reader pool, in-transaction change events (`kv.go`), event streams as rows (`stream.go`). |
-| `internal/storage` | Flat-key records (`client.go`), UUIDv7 minting, CID reverse index (`cid_resolution.go`), schema sentinel, search over `kv_field` + FTS (`search.go`), UDL store (`udl.go`, `udl_admin.go`), stats. |
+| `internal/storage` | Flat-key records (`client.go`), UUIDv7 minting, CID reverse index (`cid_resolution.go`), schema sentinel, search over `kv_field_v` + FTS (`search.go`), derived counters (`onChange`), UDL store (`udl.go`, `udl_admin.go`), stats. |
 | `internal/cid` | CID parsing + rank ladder for canonical-CID selection (`cid-rank-vectors.json`, guarded by the meta-root `scripts/check-cid-vectors.sh`). |
 | `internal/identity` | Multi-account secp256k1 keystore, challenge/proof-of-possession, signature verification. |
 | `internal/api` | HTTP server + all handlers + SSE event endpoints + search matchers + `/api/stats`. |