feat(8.0): API simplification — remove neural()/Db.search, one storage path key, integration→0

8.0 RC cleanup toward "one place per thing, zero-config, no deprecation":

- Remove the `brain.neural()` clustering namespace (ImprovedNeuralAPI + the dead
  legacy NeuralAPI + the neural CLI + neural-only types). Similarity is `find({vector})`
  / `similar({to})`; attribute grouping is the aggregation `GROUP BY` engine. The separate
  entity-extraction / smart-import feature (NeuralImport, NeuralEntityExtractor, SmartExtractor,
  NaturalLanguageProcessor, `brain.extract()`/`brain.nlp()`) is kept.
- Remove `Db.search()`; `find()` is the one query verb (accepts a bare string or FindParams).
  Fix the bundled MCP client, which called a non-existent `brain.search(query, limit)` →
  now `find({ query, limit })`.
- Storage config: collapse to one canonical top-level `path` key. The pre-8.0 aliases
  (`rootDirectory`, `options.*`, `fileSystemStorage.*`) are removed and now THROW with the
  exact rename instead of silently defaulting to `./brainy-data` on upgrade. A single resolver
  feeds createStorage, the 7.x→8.0 migration probe, and the plugin-factory handoff, so a native
  storage provider resolves the identical root (no split-brain).
- Fix `similar({ threshold })`: the min-similarity filter was silently dropped; it is now
  applied as a post-filter on `result.score` (the documented way to bound semantic results).
- Fix `vfs.rename()` on a directory: child path updates spread the entity vector into `update()`
  and failed dimension validation; they are metadata-only updates now.
- Fix `vfs.move()`: copy+delete orphaned the content-addressed content blob (the destination
  shared the source hash, then unlink removed it). `move()` now delegates to `rename()` — an
  in-place path change that preserves the blob and the entity id, for files and directories.
- Fix streaming import: the bulk fast path never flushed mid-import nor signalled queryability.
  Entity writes are now chunked by a progressive flush interval (100 → 1000 → 5000); each chunk
  flushes and emits `progress.queryable`, so imported data is queryable during the import.
- Sweep all docs, comments, and JSDoc for the removed/changed APIs.

Integration suite: 49 files / 588 passed / 0 failed. Unit: 80 files / 1456 passed, no type errors.

tests/benchmarks/performance-comprehensive.js

@@ -63,7 +63,7 @@ async function runV2Benchmark() {
   console.log('Testing vector search...')
   const start3 = Date.now()
   for (let i = 0; i < 10; i++) {
-    await brain.search(vectors[1000 + i], 10)
+    await brain.find({ vector: vectors[1000 + i], limit: 10 })
   }
   const searchTime = Date.now() - start3
   results.search = Math.round(10 / (searchTime / 1000))

tests/benchmarks/performance-v3.js

@@ -45,7 +45,7 @@ async function benchmarkV2() {
   
   // Test 3: Search operations
   const start3 = performance.now()
-  await brain.search({
+  await brain.find({
     query: new Array(384).fill(0).map(() => Math.random()),
     limit: 10
   })

tests/benchmarks/quick-benchmark-v3.js

@@ -92,22 +92,6 @@ async function testV3() {
   console.log(`✅ Batch add 50 items: ${batchTime}ms (${Math.round(50 / (batchTime / 1000))} ops/sec)`)
   console.log(`   Success: ${batchResult.successful.length}, Failed: ${batchResult.failed.length}`)
   
-  // Test 7: Neural API
-  console.log('\n🧠 Testing Neural API...')
-  try {
-    const neural = brain.neural()
-    const start7 = Date.now()
-    const clusters = await neural.clusters({
-      items: ids.slice(0, 20),
-      k: 3
-    })
-    const clusterTime = Date.now() - start7
-    console.log(`✅ Cluster 20 items into 3 groups: ${clusterTime}ms`)
-    console.log(`   Clusters: ${clusters.map(c => c.items.length).join(', ')} items`)
-  } catch (e) {
-    console.log(`⚠️ Neural API: ${e.message}`)
-  }
-  
   // Test 8: Streaming Pipeline
   console.log('\n🌊 Testing Streaming Pipeline...')
   const { Pipeline } = await import('../dist/streaming/pipeline.js')