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/vfs/ROADMAP.md

@@ -65,27 +65,6 @@ const diff = await vfs.diffVersions('/important-doc.md', v1, v2)
 **Status:** Planned
 **Effort:** 4-5 weeks
 
-### Distributed Filesystem
-Mount remote Brainy instances for federated file access.
-
-```typescript
-// Planned API (not yet implemented)
-await vfs.mount('/remote-team', {
-  type: 'brainy-remote',
-  url: 'https://team-brainy.example.com',
-  credentials: {...}
-})
-
-// Federated search across mounted instances
-const results = await vfs.search('project docs', { includeMounted: true })
-
-// Sync directories
-await vfs.sync('/local/docs', '/remote-team/docs')
-```
-
-**Status:** Planned
-**Effort:** 6-8 weeks
-
 ### Backup & Recovery API
 Built-in backup and recovery operations.
 
@@ -215,12 +194,6 @@ Vite integration with VFS for semantic module resolution.
 
 ## Far Future (v5.0+)
 
-### Automatic Node Discovery
-Zero-config multi-node setup with automatic discovery via UDP broadcast, Kubernetes DNS, or cloud provider APIs.
-
-### Automatic Failover
-Health monitoring and automatic failover in distributed deployments.
-
 ### Cloud Provider Auto-Detection
 ```typescript
 // Far future concept