refactor(8.0)!: remove distributed clustering subsystem — inert/orphaned, scale is single-process + native provider

The distributed-clustering subsystem never ran in production: it was inert,
orphaned dead code (faked consensus, stub replication, no live wiring, and it
did not interoperate with the 8.0 Db API). Brainy 8.0 is a single-process
library. Scale is single-process + the optional native provider
(@soulcraft/cortex, on-disk DiskANN to 10B+ vectors) + per-tenant pools +
horizontal read scaling (many reader processes, one writer).

Removed:
- src/distributed/ entirely (coordinator, shardManager, cacheSync,
  readWriteSeparation, queryPlanner, healthMonitor, configManager,
  hashPartitioner, shardMigration, domainDetector, storageDiscovery, http/network
  transports). ReaderMode/HybridMode relocated to src/storage/operationalModes.ts
  (slimmed to the live surface).
- src/types/distributedTypes.ts; config.distributed field + JSDoc;
  coreTypes distributedConfig; memoryStorage distributedConfig persistence.
- DistributedRole enum + src/config/distributedPresets.ts and the orphaned
  src/config/extensibleConfig.ts (config/augmentation registry built on removed
  cloud adapters + distributed presets), plus their src/index.ts re-exports.
- 13 BRAINY_* cluster env vars; the storage setDistributedComponents hook;
  enableDistributedSearch (dead config flag); the metadata partition field;
  the distributed_ reserved key prefix.
- Orphaned src/storage/readOnlyOptimizations.ts (zero importers).
- Tests targeting the subsystem: distributed-demo, distributed-cluster helper,
  distributed-transactions, sharding-transactions.
- Docs: EXTENDING_STORAGE.md (deleted); scrubbed distributed/cluster/Raft/
  shard-manager/multi-node prose from v3-features, enterprise-for-everyone,
  augmentations-actual, complete-feature-list, vfs/README, vfs/ROADMAP,
  vfs/VFS_CORE, capacity-planning, transactions, MIGRATION-V3-TO-V4,
  storage-architecture; reframed scale prose to the 8.0 model.

Kept: src/storage/sharding.ts (local-disk 256-bucket directory sharding via
getShardIdFromUuid — used live by baseStorage, unrelated to clustering);
the multi-process mode: 'reader' | 'writer' roles; semantic/HNSW clustering.

RELEASES.md: added a removed-surfaces row documenting the cut and the 8.0
scale model.

docs/features/complete-feature-list.md

@@ -66,7 +66,7 @@ import { BatchProcessingAugmentation } from 'brainy'
 ```typescript
 import { ConnectionPoolAugmentation } from 'brainy'
 // Auto-scaling connection management
-// Optimized for distributed operations
+// Optimized for high-concurrency workloads
 ```
 
 ### 7. Request Deduplicator ✅
@@ -100,8 +100,7 @@ import { MemoryStorageAugmentation } from 'brainy'
 ### 11. Server Search Conduit ✅
 ```typescript
 import { ServerSearchConduitAugmentation } from 'brainy'
-// Distributed query execution
-// Load balancing across nodes
+// Forwards queries to a remote Brainy server
 ```
 
 ### 12. Neural Import ✅
@@ -155,7 +154,9 @@ await brain.init()
 - **No environment variables needed**
 - **Works in all environments** (Node, Browser, Workers)
 
-## 🏢 Distributed Operation Modes
+## 🏢 Operation Modes
+
+Run many reader processes against one shared on-disk store with a single writer.
 
 ### Reader Mode ✅
 ```typescript
@@ -374,7 +375,7 @@ await brain.init()
 - ✅ All engines (vector, graph, field, neural)
 - ✅ All augmentations (12+)
 - ✅ All storage adapters
-- ✅ All distributed modes
+- ✅ Reader / writer / hybrid operation modes
 - ✅ Complete statistics
 - ✅ GPU support
 - ✅ No feature limitations