First VectorStore implementation. Per-model Lance tables under
config.storage.vector_dir, two-phase upsert (SQLite-pending → Lance
MergeInsert → SQLite-committed) with crash-safe retry, search via
cosine distance with the spec's score-shift (preserves negative
similarity ranking signal that clamping would crush).

V003 migration:
- Adds status (CHECK constraint pending|committed|tombstone, default
  pending) and vector_committed columns to embedding_records.
- BEFORE DELETE trigger on chunks flips dependent rows to tombstone.
  Currently overshadowed by V001's ON DELETE CASCADE FK; trigger UPDATE
  runs first then row vanishes via CASCADE. Spec-faithful tombstone
  preservation requires recreating embedding_records to drop the
  CASCADE — deferred to a P+ migration since no production rows exist
  yet (P3-3 is the first writer). V003 SQL comment explains.

LanceVectorStore:
- ensure_table is idempotent: opens existing or creates with the
  Arrow schema (chunk_id, doc_id, embedding FixedSizeList<Float32,
  dim>, model_id, embedding_version, text, heading_path, created_at).
- IndexId computed via id_for_index with collection="chunk_embeddings",
  index_kind="flat", params_hash = blake3(descriptor JSON). Schema
  bumps automatically rotate the IndexId.
- upsert: phase-1 INSERT OR REPLACE INTO embedding_records (status=
  'pending') in a single SQLite tx; phase-2 Lance MergeInsert keyed
  on chunk_id (idempotent re-run); phase-3 UPDATE status='committed',
  vector_committed=1. If phase-2 fails the rows stay 'pending' and
  the next upsert call retries idempotently.
- search joins embedding_records WHERE status='committed' so partial-
  write rows never surface. Cosine distance from Lance ∈ [0, 2] →
  similarity = 1 - distance ∈ [-1, 1] → score = (similarity + 1)/2 ∈
  [0, 1]. NaN coerced to 0 with tracing::warn. Filter by SearchFilters
  via SqliteStore::filter_chunks (added in this commit).
- Sync trait + async LanceDB bridged by an embedded current-thread
  tokio runtime. Doc-comment on the struct flags the "do NOT call
  from inside another tokio runtime" panic (block_on cannot nest).
  kb-app's job scheduler is sync today.

kb-store-sqlite additions:
- pub fn put_embedding_records_pending(&[EmbeddingRecordRow]) — phase-1
  INSERT OR REPLACE (status='pending', vector_committed=0).
- pub fn mark_embedding_records_committed(&[EmbeddingId]) — phase-3
  single UPDATE … WHERE embedding_id IN (?, ?, …) via
  params_from_iter, guarded by WHERE status='pending' so tombstones
  don't get clobbered.
- pub fn filter_chunks(&[ChunkId], &SearchFilters) → Vec<ChunkId>
  consolidates the JOIN against documents/document_tags/
  embedding_records + path_glob via globset. Lets kb-store-vector
  honor SearchFilters without depending on rusqlite or globset
  directly. (kb-search's filter logic is structurally different —
  interleaved with the FTS5 SELECT — so it stays as-is for now;
  consolidation is a P+ refactor.)
- 4 new unit tests cover the phase-1 round-trip, empty batch,
  replay reset of pending rows, and the WHERE-status-pending guard.

Tests:
- 9 lib unit tests in kb-store-vector covering paths/sanitization,
  arrow_batch dim validation + descriptor hash, bm25-style cosine
  score shift math.
- 4 new kb-store-sqlite unit tests on filter_chunks (committed-only,
  tags/lang/trust/path_glob, order preservation, empty input).
- 4 new kb-store-sqlite unit tests on the embedding_records helpers.
- 8 integration tests in upsert_search.rs and 1 snapshot test marked
  #[ignore = "requires AVX-capable hardware (LanceDB)"]. They invoke
  require_avx_or_panic() at the top of each body so a missing-AVX
  --ignored run fails loudly instead of silently passing. This dev
  host (qemu64 model) lacks AVX so these were NOT exercised end-to-
  end here — first CI lane on AVX hardware will validate them.
- Snapshot fixture tests/fixtures/vector/run-1.json is a placeholder
  with an _comment marker. Snapshot test panics until the placeholder
  is replaced via KB_UPDATE_SNAPSHOTS=1 on AVX hardware.
- Workspace 241 passed, 19 ignored, 0 failed; cargo clippy --workspace
  --all-targets -- -D warnings clean.

Allowed deps respected (kb-core, kb-config, kb-store-sqlite, lancedb,
arrow + arrow-array + arrow-schema, serde, serde_json, tracing,
thiserror) plus forced waivers — anyhow (trait return type), tokio
+ futures (LanceDB async-only API), blake3 (params_hash). rusqlite
and globset are NOT direct deps of kb-store-vector — confirmed via
cargo metadata --no-deps. rusqlite stays in [dev-dependencies] for
the test fixture seeder only.

Out of scope: IVF/PQ index tuning (P+), image vectors (P6), kb-app
embed_index orchestration (P3-4 facade).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

@@ -0,0 +127,4 @@
+                    AND embedding_id IN ({placeholders})"
+            );
+            tx.execute(&sql, params_from_iter(embedding_ids.iter()))
+                .map_err(StoreError::from)?;

@@ -0,0 +1,452 @@
+//! Chunk-level filter helpers shared between retrievers.

@@ -0,0 +67,4 @@
+    runtime: Runtime,
+    connection: Connection,
+    sqlite: Arc<SqliteStore>,
+    /// Resolved absolute path to the Lance root. Kept for diagnostics

@@ -0,0 +237,4 @@
+        let table_schema = self
+            .runtime
+            .block_on(async { table.schema().await.context("read table schema") })?;
+        Self::check_dim(&table_schema, dim)?;

@@ -0,0 +434,4 @@
+            .as_any()
+            .downcast_ref::<StringArray>()
+            .context("text wrong type")?;
+        let heading_path_str = batch

@@ -0,0 +32,4 @@
+//! the tests stay independent of kb-parse-md / kb-normalize / kb-chunk
+//! and so we can construct adversarial fixtures (filtered tags,
+//! mismatched langs) without reproducing a Markdown round-trip.
+

@@ -0,0 +1,4 @@
+{

@@ -0,0 +35,4 @@
+-- runs", so this UPDATE will land a `tombstone` value that is
+-- immediately followed by the CASCADE removing the row. The trigger is
+-- therefore best-effort under the current FK; the only path that
+-- actually preserves the tombstone is to drop the CASCADE (table

@@ -0,0 +1,34 @@
+[