refactor(8.0): rename HNSWIndex class → JsHnswVectorIndex (scaffold step 3)

Step 3 of the brainy 8.0 rename scaffolding. The class name now matches
its role: the JS HNSW implementation of the VectorIndexProvider contract.
Per planning § 2.3: this is NOT cosmetic — leaving HNSWIndex when the
public contract is VectorIndexProvider creates a confusing read at the
implementation layer.

CHANGES

Repo-wide mechanical rename: HNSWIndex → JsHnswVectorIndex across 52
references in src/ + 5 references in tests/ via sed. Class declaration,
imports, JSDoc, comments, and identifiers all updated.

src/index.ts
- Primary public export: JsHnswVectorIndex (the new name).
- Backwards-compat alias: `export const HNSWIndex = JsHnswVectorIndex`
  with @deprecated note. Removed in the final 8.0 cleanup commit.

NO-OP scope

No behavioural change. The class is exactly the same; only the name
moved. Tests + build green.

VERIFICATION

- npx tsc --noEmit: clean
- npm test: 1468 / 1468 unit

src/triple/TripleIntelligenceSystem.ts

@@ -13,7 +13,7 @@
  * - Fusion: O(k log k) where k = result count
  */
 
-import { HNSWIndex } from '../hnsw/hnswIndex.js'
+import { JsHnswVectorIndex } from '../hnsw/hnswIndex.js'
 import { MetadataIndexManager } from '../utils/metadataIndex.js'
 import { Vector } from '../coreTypes.js'
 import { NounType } from '../types/graphTypes.js'
@@ -230,7 +230,7 @@ class QueryPlanner {
  */
 export class TripleIntelligenceSystem {
   private metadataIndex: MetadataIndexManager
-  private hnswIndex: HNSWIndex
+  private hnswIndex: JsHnswVectorIndex
   private graphIndex: GraphAdjacencyIndex
   private metrics: PerformanceMetrics
   private planner: QueryPlanner
@@ -239,7 +239,7 @@ export class TripleIntelligenceSystem {
 
   constructor(
     metadataIndex: MetadataIndexManager,
-    hnswIndex: HNSWIndex,
+    hnswIndex: JsHnswVectorIndex,
     graphIndex: GraphAdjacencyIndex,
     embedder: (text: string) => Promise<Vector>,
     storage: any