Dual-Graph Router

Route an incoming request to the VERTICAL knowledge graph (what the agent knows — a single relationship/temporal traversal), the HORIZONTAL workflow graph (how the agent acts — a decomposed multi-step process), BOTH (a workflow whose nodes query the knowledge graph and write results back), or UNROUTABLE (neither fits — ask for clarification). Implements the central dual-graph distinction of Agentic GraphRAG Ch2 and the "Where the Two Graphs Meet" bidirectional interaction. Use when an agent receives an on-call request and must decide whether it is a knowledge lookup or a process. NOT for building the workflow DAG itself (that is harness-node-splitter / investigation-dag-p…