feat(memory): enable KnowledgeGraph by default, add disabled opt-out flag

Graph now activates automatically when CognitiveMemoryManager initializes,
providing spreading activation (Collins & Quillian), Hebbian co-activation
learning, and graph-boosted retrieval scoring out of the box. Set
graph.disabled=true to opt out. All MemoryGraphConfig fields are now optional
with sensible defaults exported as DEFAULT_GRAPH_CONFIG.

Author: jddunn

src/memory/CognitiveMemoryManager.ts

@@ -27,6 +27,7 @@ import {
   DEFAULT_ENCODING_CONFIG,
   DEFAULT_DECAY_CONFIG,
   DEFAULT_BUDGET_ALLOCATION,
+  DEFAULT_GRAPH_CONFIG,
 } from './core/config.js';
 import { computeEncodingStrength, buildEmotionalContext } from './core/encoding/EncodingModel.js';
 import {
@@ -256,9 +257,13 @@ export class CognitiveMemoryManager implements ICognitiveMemoryManager {
       config.featureDetectionLlmInvoker
     );
 
-    // --- Batch 2: Memory Graph ---
-    if (config.graph) {
-      const backend = config.graph.backend ?? 'knowledge-graph';
+    // --- Memory Graph (enabled by default, opt-out via disabled: true) ---
+    // The knowledge graph powers spreading activation (Collins & Quillian model),
+    // Hebbian co-activation learning ("neurons that fire together wire together"),
+    // and graph-boosted retrieval scoring. It is fundamental to associative memory.
+    if (config.graph?.disabled !== true) {
+      const graphConfig = { ...DEFAULT_GRAPH_CONFIG, ...config.graph };
+      const backend = graphConfig.backend;
       if (backend === 'graphology') {
         this.graph = new GraphologyMemoryGraph();
       } else {

src/memory/core/config.ts

@@ -78,19 +78,50 @@ export interface ReflectorConfig {
   llmInvoker?: (systemPrompt: string, userPrompt: string) => Promise<string>;
 }
 
+/**
+ * Configuration for the memory graph subsystem.
+ *
+ * The memory graph powers spreading activation (Collins & Quillian model),
+ * Hebbian co-activation learning ("neurons that fire together wire together"),
+ * conflict detection, clustering, and graph-boosted retrieval scoring.
+ *
+ * Enabled by default when CognitiveMemoryManager is initialized.
+ * Set `disabled: true` to opt out entirely.
+ */
 export interface MemoryGraphConfig {
-  /** Which backend to use. @default 'knowledge-graph' */
-  backend: 'graphology' | 'knowledge-graph';
+  /**
+   * Set to true to disable the memory graph entirely.
+   * When disabled, spreading activation, Hebbian co-activation,
+   * and graph-based retrieval boosting are all skipped.
+   * @default false
+   */
+  disabled?: boolean;
+  /** Which graph backend to use. @default 'knowledge-graph' */
+  backend?: 'graphology' | 'knowledge-graph';
   /** Max hops for spreading activation. @default 3 */
-  maxDepth: number;
-  /** Activation decay per hop. @default 0.5 */
-  decayPerHop: number;
-  /** Minimum activation to continue spreading. @default 0.1 */
-  activationThreshold: number;
-  /** Hebbian learning rate for co-activation edge strengthening. @default 0.1 */
-  hebbianLearningRate: number;
+  maxDepth?: number;
+  /** Activation decay per hop (0-1). @default 0.5 */
+  decayPerHop?: number;
+  /** Minimum activation to continue spreading (0-1). @default 0.1 */
+  activationThreshold?: number;
+  /** Hebbian learning rate for co-activation edge strengthening (0-1). @default 0.1 */
+  hebbianLearningRate?: number;
 }
 
+/**
+ * Default memory graph configuration.
+ * Graph is enabled by default with the KnowledgeGraph backend,
+ * providing spreading activation and Hebbian learning out of the box.
+ */
+export const DEFAULT_GRAPH_CONFIG: Required<Omit<MemoryGraphConfig, 'disabled'>> & { disabled: false } = {
+  disabled: false,
+  backend: 'knowledge-graph',
+  maxDepth: 3,
+  decayPerHop: 0.5,
+  activationThreshold: 0.1,
+  hebbianLearningRate: 0.1,
+};
+
 export interface ConsolidationConfig {
   /** How often to run consolidation (ms). @default 3_600_000 (1 hour) */
   intervalMs: number;