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.

README.md

@@ -311,7 +311,7 @@ const brain = new Brainy()
 
 ```javascript
 const brain = new Brainy({
-  storage: { type: 'filesystem', rootDirectory: './data' }
+  storage: { type: 'filesystem', path: './data' }
 })
 ```
 
@@ -323,7 +323,7 @@ await db.persist('/backups/2026-06-11')   // instant hard-link snapshot
 await db.release()
 
 const snapshot = await Brainy.load('/backups/2026-06-11')  // read-only Db
-const hits = await snapshot.search('quarterly invoices')
+const hits = await snapshot.find({ query: 'quarterly invoices' })
 await snapshot.release()
 ```
 
@@ -405,13 +405,13 @@ existing one.
 
 ```typescript
 // Live application — writer mode is the default
-const brain = new Brainy({ storage: { type: 'filesystem', rootDirectory: '/data/brain' } })
+const brain = new Brainy({ storage: { type: 'filesystem', path: '/data/brain' } })
 await brain.init()
 
 // Out-of-band diagnostics from a separate process — safe to run while the
 // writer is live
 const reader = await Brainy.openReadOnly({
-  storage: { type: 'filesystem', rootDirectory: '/data/brain' }
+  storage: { type: 'filesystem', path: '/data/brain' }
 })
 await reader.requestFlush({ timeoutMs: 5000 })
 const stats = await reader.stats()