docs: SelectedNodeData is flat, so the node type is read directly off it

docs/superpowers/plans/2026-08-04-tier-1-nodes.md

@@ -911,7 +911,7 @@ Replace `saveNodeConfig` (lines 1628-1641):
   const saveNodeConfig = () => {
     if (!selectedNodeData) return
     const nodeId = selectedNodeData.id
-    const nodeDef = nodeDefsMap[selectedNodeData.data.type]
+    const nodeDef = nodeDefsMap[selectedNodeData.type]
 
     setNodes((nds) =>
       nds.map((n) =>