refactor: Replace knowledge graph with session clustering system

Remove legacy knowledge graph and evolution tracking features,
introduce new session clustering model for Core Memory.

Changes:
- Remove knowledge_graph, knowledge_graph_edges, evolution_history tables
- Add session_clusters, cluster_members, cluster_relations tables
- Add session_metadata_cache for metadata caching
- Add new interfaces: SessionCluster, ClusterMember, ClusterRelation, SessionMetadataCache
- Add CRUD methods for cluster management
- Add session metadata upsert and search methods
- Remove extractKnowledgeGraph, getKnowledgeGraph, trackEvolution methods
- Remove API routes for /knowledge-graph, /evolution, /graph
- Add database migration to clean up old tables
- Update generateClusterId() for CLST-* ID format

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ccw/src/commands/core-memory.ts

@@ -71,9 +71,6 @@ async function importAction(text: string): Promise<void> {
 
     console.log(chalk.green(`✓ Created memory: ${memory.id}`));
 
-    // Extract knowledge graph
-    store.extractKnowledgeGraph(memory.id);
-
     // Notify dashboard
     notifyRefreshRequired('memory').catch(() => { /* ignore */ });