refactor(8.0): final cleanup — drop HnswProvider alias + config.hnsw + 'hnsw' surface (scaffold step 6)

Step 6 of the brainy 8.0 rename scaffolding. Removes every legacy 'hnsw'-
flavoured public name introduced as a compat shim in steps 1-5. The
algorithm-neutral surface is now the only surface.

REMOVED — PHASE A (type aliases)

src/plugin.ts
- Removed `export type HnswProvider = VectorIndexProvider` alias.
- Removed `export type DiskAnnProvider = VectorIndexProvider` alias.

src/index.ts
- Removed `export const HNSWIndex = JsHnswVectorIndex` alias.

src/types/brainy.types.ts
- Removed `BrainyStats.indexHealth.hnsw` field (the new `vector` field
  carries the same boolean).

src/brainy.ts
- `stats()` no longer emits the legacy `hnsw` field on `indexHealth`.

REMOVED — PHASE B (storage adapter rename, 8 adapters)

Repo-wide rename: `saveHNSWData` → `saveVectorIndexData` and
`getHNSWData` → `getVectorIndexData` across:

- src/storage/adapters/baseStorageAdapter.ts (abstract declarations)
- src/storage/adapters/fileSystemStorage.ts
- src/storage/adapters/gcsStorage.ts
- src/storage/adapters/r2Storage.ts
- src/storage/adapters/s3CompatibleStorage.ts
- src/storage/adapters/azureBlobStorage.ts
- src/storage/adapters/opfsStorage.ts
- src/storage/adapters/memoryStorage.ts
- src/storage/adapters/historicalStorageAdapter.ts
- src/brainy.ts (call sites)
- src/hnsw/hnswIndex.ts + src/hnsw/typeAwareHNSWIndex.ts (call sites)

The default-delegation wrappers added in scaffold step 4 are removed
(would have been duplicate declarations after the rename).

REMOVED — PHASE C (cache category 'hnsw')

src/utils/unifiedCache.ts
- Cache-category union narrowed from
    'hnsw' | 'vectors' | 'metadata' | 'embedding' | 'other'
  to
    'vectors' | 'metadata' | 'embedding' | 'other'
- typeAccessCounts, typeSizes, typeCounts, accessRatios, sizeRatios,
  and the fairness-check iterator all drop the 'hnsw' key.
- Per planning § 2.5: pre-8.0 'hnsw' cache entries are an in-memory
  category. Cache is rebuildable; entries naturally don't exist after
  a restart, so no migration path is needed.

src/hnsw/hnswIndex.ts
- 3 cache.set() call sites migrated from category 'hnsw' to 'vectors'.
- Cache key prefix `hnsw:vector:` → `vector:`.
- typeCounts/typeSizes/typeAccessCounts accessor renames
  `.hnsw` → `.vectors`.

tests/unit/utils/unifiedCache-eviction.test.ts
- Test fixtures updated: cache.set(..., 'hnsw', ...) → cache.set(..., 'vectors', ...).
- Stats assertion `stats.typeSizes.hnsw` → `stats.typeSizes.vectors`.

REMOVED — PHASE D (config.hnsw)

src/types/brainy.types.ts
- Removed `BrainyConfig.hnsw` field entirely. The 8.0 surface is
  `BrainyConfig.vector.{recall, quantization, vectorStorage, advanced}`.

src/brainy.ts
- normalizeConfig() no longer emits a `hnsw` field on Required<BrainyConfig>.
- setupIndex() rewired:
  - Reads from `this.config.vector` (not `this.config.hnsw`).
  - Calls `resolveJsHnswConfig(this.config.vector)` to translate the
    `recall` preset into M / efConstruction / efSearch knobs (with
    `advanced.hnsw` overrides winning when supplied).
- Imports `resolveJsHnswConfig` from './utils/recallPreset.js'.

NOT IN THIS COMMIT (deliberately)

- Persisted file path migration `_system/hnsw-*.json` →
  `_system/vector-index-*.json`. Requires dual-read logic on boot
  across 8 storage adapters. Per integration doc lines 531-539:
  "Reader accepts either spelling on load; writer emits the new spelling
  only; brains self-migrate on the next persist after upgrade." This is
  a separate body of work and lands in a follow-up commit before 8.0 GA.
- `config.hnswPersistMode` top-level field is unchanged. It's not in
  the rename inventory; a future commit can fold it into
  `config.vector.persistMode` if desired.
- strictConfig enforcement wiring. The field is accepted by
  normalizeConfig() with default 'warn'; the actual warning emission at
  knob-mismatch sites lands when the config-resolution layer is touched
  for the persisted-path migration.

VERIFICATION

- npx tsc --noEmit: clean
- npm test: 1468 / 1468 unit (one test fixture updated to use the new
  category name; assertion still passes after fixture rename)
- npm run build: clean

The 8.0 PR's user-facing surface is now algorithm-neutral end-to-end:
VectorIndexProvider, config.vector.recall, JsHnswVectorIndex,
saveVectorIndexData, 'vectors' cache category, indexHealth.vector,
strictConfig — all standalone. No legacy 'hnsw' name remains in any
public type or method signature.

src/brainy.ts

@@ -110,6 +110,7 @@ import type { MigrationPreview, MigrationResult, MigrateOptions } from './migrat
 import { AggregationIndex } from './aggregation/AggregationIndex.js'
 import { AggregateMaterializer } from './aggregation/materializer.js'
 import type { AggregateDefinition, AggregateQueryParams, AggregateResult } from './types/brainy.types.js'
+import { resolveJsHnswConfig } from './utils/recallPreset.js'
 
 /**
  * Stopwords for semantic highlighting
@@ -3615,7 +3616,7 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     }
 
     // OPTIMIZATION: Defer HNSW persistence during batch insert.
-    // Without this, each add() triggers ~16-20 neighbor saveHNSWData calls
+    // Without this, each add() triggers ~16-20 neighbor saveVectorIndexData calls
     // (each a read→gzip→atomic-write cycle). For 450 items that's ~8,100
     // individual storage writes. Deferred mode collects dirty node IDs and
     // flushes once at the end — deduplicating repeated neighbor updates.
@@ -6270,13 +6271,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       relationsByType,
       fieldRegistry,
       indexHealth: await (async () => {
-        // 8.0 rename: `vector` is the canonical name; `hnsw` is a compat
-        // alias that's removed in the final 8.0 cleanup commit.
-        const vectorHealthy = this.index.size() > 0 || entityCount === 0
         const graphSize = await this.graphIndex.size()
         return {
-          hnsw: vectorHealthy,
-          vector: vectorHealthy,
+          vector: this.index.size() > 0 || entityCount === 0,
           metadata: metadataStats.totalEntries > 0 || entityCount === 0,
           graph: graphSize > 0 || relationCount === 0
         }
@@ -9078,16 +9075,21 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    * - Local storage (FileSystem/Memory/OPFS): 'immediate' (already fast)
    */
   private setupIndex(): JsHnswVectorIndex {
+    // 8.0 config surface: config.vector.{quantization, vectorStorage, recall, advanced}.
+    // The recall preset translates to HNSW knobs (M / efConstruction / efSearch) via
+    // resolveJsHnswConfig; explicit advanced.hnsw overrides win.
+    const recallKnobs = resolveJsHnswConfig(this.config.vector)
+    const vectorCfg = this.config.vector
     const indexConfig = {
       ...this.config.index,
+      ...recallKnobs,
       distanceFunction: this.distance,
-      // Wire HNSW optimization config (v7.11.0)
-      quantization: this.config.hnsw?.quantization ? {
-        enabled: this.config.hnsw.quantization.enabled ?? false,
-        bits: this.config.hnsw.quantization.bits ?? 8,
-        rerankMultiplier: this.config.hnsw.quantization.rerankMultiplier ?? 3
+      quantization: vectorCfg?.quantization ? {
+        enabled: vectorCfg.quantization.enabled ?? false,
+        bits: vectorCfg.quantization.bits ?? 8,
+        rerankMultiplier: vectorCfg.quantization.rerankMultiplier ?? 3
       } : undefined,
-      vectorStorage: this.config.hnsw?.vectorStorage
+      vectorStorage: vectorCfg?.vectorStorage
     }
 
     const persistMode = this.resolveHNSWPersistMode()
@@ -9292,8 +9294,6 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       reservedQueryMemory: config?.reservedQueryMemory ?? undefined as any,
       // HNSW persistence mode - undefined = smart default in setupIndex
       hnswPersistMode: config?.hnswPersistMode ?? undefined as any,
-      // HNSW optimization options (v7.11.0) — deprecated in 8.0, see `vector` below.
-      hnsw: config?.hnsw ?? undefined as any,
       // Vector index configuration (8.0) — algorithm-neutral surface with
       // `recall` preset. See BRAINY-8.0-RENAME-COORDINATION § A.2.
       vector: config?.vector ?? undefined as any,
@@ -9464,7 +9464,7 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    * storage adapter directly, so the codec is engaged on cloud adapters too.
    * Format convergence is lazy: pre-2.4.0 nodes load via the legacy path,
    * then the next dirty save writes the compressed form (and the legacy
-   * field of saveHNSWData becomes empty), so all reads converge over time
+   * field of saveVectorIndexData becomes empty), so all reads converge over time
    * without an explicit migration step.
    */
   private wireConnectionsCodec(): void {