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.

src/types/brainy.types.ts

@@ -1206,25 +1206,6 @@ export interface BrainyConfig {
       }
     | StorageAdapter
 
-  /**
-   * Distributed-cluster configuration. **Explicit opt-in only** — Brainy
-   * never auto-enables cluster mode from environment heuristics (a single
-   * production process is the 90th-percentile deployment). Set
-   * `enabled: true` (or the `BRAINY_DISTRIBUTED=true` env var) to activate;
-   * the remaining fields then default sensibly (64 shards, 3 replicas,
-   * raft consensus, http transport, hostname-derived nodeId).
-   */
-  distributed?: {
-    enabled: boolean
-    nodeId?: string
-    nodes?: string[]           // Other nodes in cluster
-    coordinatorUrl?: string    // Coordinator endpoint
-    shardCount?: number        // Number of shards (default: 64)
-    replicationFactor?: number // Number of replicas (default: 3)
-    consensus?: 'raft' | 'none' // Consensus mechanism
-    transport?: 'tcp' | 'http' | 'udp'
-  }
-
   /**
    * Disable the automatic index rebuild check during `init()`. By default
    * Brainy auto-decides from dataset size: small datasets rebuild missing

src/types/distributedTypes.ts

@@ -1,236 +0,0 @@
-/**
- * Distributed types for Brainy
- * Defines types for distributed operations across multiple instances
- */
-
-export type InstanceRole = 'reader' | 'writer' | 'hybrid'
-
-export type PartitionStrategy = 'hash' | 'semantic' | 'manual'
-
-export interface DistributedConfig {
-  /**
-   * Enable distributed mode
-   * Can be boolean for auto-detection or specific configuration
-   */
-  enabled?: boolean | 'auto'
-  
-  /**
-   * Role of this instance in the distributed system
-   * - reader: Read-only access, optimized for queries
-   * - writer: Write-focused, handles data ingestion
-   * - hybrid: Can both read and write (requires coordination)
-   */
-  role?: InstanceRole
-  
-  /**
-   * Unique identifier for this instance
-   * Auto-generated if not provided
-   */
-  instanceId?: string
-  
-  /**
-   * Path to shared configuration file in S3
-   * Default: '_brainy/config.json'
-   */
-  configPath?: string
-  
-  /**
-   * Heartbeat interval in milliseconds
-   * Default: 30000 (30 seconds)
-   */
-  heartbeatInterval?: number
-  
-  /**
-   * Config check interval in milliseconds
-   * Default: 10000 (10 seconds)
-   */
-  configCheckInterval?: number
-  
-  /**
-   * Instance timeout in milliseconds
-   * Instances not seen for this duration are considered dead
-   * Default: 60000 (60 seconds)
-   */
-  instanceTimeout?: number
-}
-
-export interface SharedConfig {
-  /**
-   * Configuration version for compatibility checking
-   */
-  version: number
-  
-  /**
-   * Last update timestamp
-   */
-  updated: string
-  
-  /**
-   * Global settings that must be consistent across all instances
-   */
-  settings: {
-    /**
-     * Partitioning strategy
-     * - hash: Deterministic hash-based partitioning (recommended for multi-writer)
-     * - semantic: Group similar vectors (single writer only)
-     * - manual: Explicit partition assignment
-     */
-    partitionStrategy: PartitionStrategy
-    
-    /**
-     * Number of partitions (for hash strategy)
-     */
-    partitionCount: number
-    
-    /**
-     * Embedding model name (must be consistent)
-     */
-    embeddingModel: string
-    
-    /**
-     * Vector dimensions
-     */
-    dimensions: number
-    
-    /**
-     * Distance metric
-     */
-    distanceMetric: 'cosine' | 'euclidean' | 'manhattan'
-    
-    /**
-     * HNSW parameters (must be consistent for index compatibility)
-     */
-    hnswParams?: {
-      M: number
-      efConstruction: number
-      maxElements?: number
-    }
-  }
-  
-  /**
-   * Active instances in the distributed system
-   */
-  instances: {
-    [instanceId: string]: InstanceInfo
-  }
-  
-  /**
-   * Partition assignments (for manual strategy)
-   */
-  partitionAssignments?: {
-    [instanceId: string]: string[]
-  }
-}
-
-export interface InstanceInfo {
-  /**
-   * Instance role
-   */
-  role: InstanceRole
-  
-  /**
-   * Instance status
-   */
-  status: 'active' | 'inactive' | 'unhealthy'
-  
-  /**
-   * Last heartbeat timestamp
-   */
-  lastHeartbeat: string
-  
-  /**
-   * Optional endpoint for health checks
-   */
-  endpoint?: string
-  
-  /**
-   * Instance metrics
-   */
-  metrics?: {
-    vectorCount?: number
-    cacheHitRate?: number
-    memoryUsage?: number
-    cpuUsage?: number
-  }
-  
-  /**
-   * Assigned partitions (for manual assignment)
-   */
-  assignedPartitions?: string[]
-  
-  /**
-   * Preferred partitions (for affinity)
-   */
-  preferredPartitions?: number[]
-}
-
-export interface DomainMetadata {
-  /**
-   * Domain identifier for logical data separation
-   */
-  domain?: string
-  
-  /**
-   * Additional domain-specific metadata
-   */
-  domainMetadata?: Record<string, any>
-}
-
-export interface CacheStrategy {
-  /**
-   * Percentage of memory allocated to hot cache (0-1)
-   */
-  hotCacheRatio: number
-  
-  /**
-   * Enable aggressive prefetching
-   */
-  prefetchAggressive?: boolean
-  
-  /**
-   * Cache time-to-live in milliseconds
-   */
-  ttl?: number
-  
-  /**
-   * Enable compression to trade CPU for memory
-   */
-  compressionEnabled?: boolean
-  
-  /**
-   * Write buffer size for batching
-   */
-  writeBufferSize?: number
-  
-  /**
-   * Enable write batching
-   */
-  batchWrites?: boolean
-  
-  /**
-   * Adaptive caching based on workload
-   */
-  adaptive?: boolean
-}
-
-export interface OperationalMode {
-  /**
-   * Whether this mode can read
-   */
-  canRead: boolean
-  
-  /**
-   * Whether this mode can write
-   */
-  canWrite: boolean
-  
-  /**
-   * Whether this mode can delete
-   */
-  canDelete: boolean
-  
-  /**
-   * Cache strategy for this mode
-   */
-  cacheStrategy: CacheStrategy
-}