feat(homecore-recorder/p2): wire RuvectorSemanticIndex with hash-based embeddings (resolves ADR-132 P2)

- ruvector-core = "2.2.0" + sha2 = "0.10" as optional deps (ruvector feature)
- RuvectorSemanticIndex: in-memory VectorDB + HNSW, EMBEDDING_DIM = 8
  - embed_state: canonical "{entity_id}={state}|{attrs_json}" → SHA-256 → 8-dim unit vec
  - insert_state(state_id, state): HNSW insert keyed by SQLite rowid
  - search(query, k): embed query → top-k (state_id, score) pairs
- SemanticIndex trait: insert_state(i64, &State) + search(str, usize) replacing index_state
- Recorder.semantic: Arc<RwLock<dyn SemanticIndex>> for interior mutability
- Recorder::search_semantic(query, k): HNSW → SQLite JOIN → Vec<StateRow>
- Tests: 20 passed (was 14 at P1): determinism, unit-norm, dim, insert+search, ranking, e2e
- P3 note: swap embed_bytes for ruvector-attention; raise dim to 384

Co-Authored-By: claude-flow <ruv@ruv.net>

v2/crates/homecore-recorder/Cargo.toml

@@ -1,10 +1,12 @@
 # homecore-recorder — SQLite state history + semantic search (ADR-132)
 #
 # P1 ships: SQLite structural persistence with HA-compat schema.
-# P2 (feature-gated): ruvector-backed SemanticIndex for embedding search.
+# P2 ships: ruvector-backed SemanticIndex — hash embeddings, HNSW search (ADR-132 P2, Iter-6 track C).
+# P3 plan:  replace hash embeddings with ruvector-attention sentence embeddings (dim → 384).
 #
-# Build: cargo build -p homecore-recorder --no-default-features
-# Test:  cargo test  -p homecore-recorder --no-default-features
+# Build:     cargo build -p homecore-recorder --features ruvector
+# Test (P2): cargo test  -p homecore-recorder --features ruvector   (20 tests)
+# Test (P1): cargo test  -p homecore-recorder --no-default-features (14 tests)
 
 [package]
 name = "homecore-recorder"