refactor(convex): modularize ai generation helpers and cleanup flows

convex/ai_node_data.ts

@@ -0,0 +1,6 @@
+export function getNodeDataRecord(data: unknown): Record<string, unknown> {
+  if (data && typeof data === "object") {
+    return data as Record<string, unknown>;
+  }
+  return {};
+}