feat: add plugin system for cortex and storage adapters

Simple plugin architecture with two use cases:
1. Native acceleration (@soulcraft/brainy-cortex) — auto-detected
2. Custom storage adapters (e.g., Redis, DynamoDB)

Plugins implement BrainyPlugin interface with activate/deactivate lifecycle.
Auto-detection tries dynamic import of known packages during init().
Manual registration via brain.use(plugin) before init().

Provider keys: metadataIndex, graphIndex, entityIdMapper, cache, hnsw,
roaring, embeddings, distance, msgpack, storage:<name>

src/brainy.ts

@@ -13,7 +13,8 @@ import { BaseStorage } from './storage/baseStorage.js'
 import { StorageAdapter, Vector, DistanceFunction, EmbeddingFunction, GraphVerb } from './coreTypes.js'
 import {
   defaultEmbeddingFunction,
-  cosineDistance
+  cosineDistance,
+  getBrainyVersion
 } from './utils/index.js'
 import { embeddingManager } from './embeddings/EmbeddingManager.js'
 import { matchesMetadataFilter } from './utils/metadataFilter.js'
@@ -33,6 +34,8 @@ import { BlobStorage } from './storage/cow/BlobStorage.js'
 import { NULL_HASH } from './storage/cow/constants.js'
 import { createPipeline } from './streaming/pipeline.js'
 import { configureLogger, LogLevel } from './utils/logger.js'
+import { PluginRegistry } from './plugin.js'
+import type { BrainyPlugin, BrainyPluginContext } from './plugin.js'
 import { TransactionManager } from './transaction/TransactionManager.js'
 import {
   ValidationConfig,
@@ -142,6 +145,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     error: typeof console.error
   }
 
+  // Plugin system
+  private pluginRegistry = new PluginRegistry()
+
   // Sub-APIs (lazy-loaded)
   private _neural?: ImprovedNeuralAPI
   private _nlp?: NaturalLanguageProcessor
@@ -267,6 +273,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
         (this.storage as any).enableCOWLightweight((this.config.storage as any)?.branch || 'main')
       }
 
+      // Auto-detect and activate plugins (e.g., @soulcraft/brainy-cortex)
+      await this.loadPlugins()
+
       // Setup index now that we have storage
       this.index = this.setupIndex()
 
@@ -6534,6 +6543,51 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     await this.metadataIndex.detectAndRepairCorruption()
   }
 
+  /**
+   * Register a plugin manually.
+   *
+   * Must be called BEFORE init(). Plugins registered after init()
+   * will not be activated.
+   */
+  use(plugin: BrainyPlugin): this {
+    this.pluginRegistry.register(plugin)
+    return this
+  }
+
+  /**
+   * Get list of active plugin names.
+   */
+  getActivePlugins(): string[] {
+    return this.pluginRegistry.getActivePlugins()
+  }
+
+  /**
+   * Auto-detect and activate plugins.
+   * Called internally during init().
+   */
+  private async loadPlugins(): Promise<void> {
+    // Auto-detect installed plugins (e.g., @soulcraft/brainy-cortex)
+    const pluginPackages = (this.config as any).plugins as string[] | undefined
+    await this.pluginRegistry.autoDetect(pluginPackages || [])
+
+    // Create plugin context
+    const context: BrainyPluginContext = {
+      registerProvider: (key, impl) => this.pluginRegistry.registerProvider(key, impl),
+      version: getBrainyVersion()
+    }
+
+    // Activate all registered plugins
+    const activated = await this.pluginRegistry.activateAll(context)
+    if (activated.length > 0) {
+      // Only log if not in silent mode
+      if (!this.config.silent) {
+        for (const name of activated) {
+          console.log(`[brainy] Plugin activated: ${name}`)
+        }
+      }
+    }
+  }
+
   /**
    * Close and cleanup
    *
@@ -6547,6 +6601,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       await this.index.flush()
     }
 
+    // Deactivate plugins
+    await this.pluginRegistry.deactivateAll()
+
     // Shutdown augmentations
     const augs = this.augmentationRegistry.getAll()
     for (const aug of augs) {