feat: initial support for RAG nodes in the graph execution system

src/config/rag_cache.rs

@@ -9,6 +9,12 @@ use std::sync::{Arc, Weak};
 pub enum RagKey {
     Named(String),
     Agent(String),
+    /// A `rag` node's per-node knowledge base, keyed by owning agent name
+    /// and node id.
+    GraphNode {
+        agent: String,
+        node: String,
+    },
 }
 
 #[derive(Default)]