fix(network): force re-render on undo/redo so canUndo/canRedo stay accurate

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/NetworkDiagrams/DiagramEditor.tsx

@@ -1,4 +1,4 @@
-import { useState, useCallback, useEffect, useRef } from 'react'
+import { useState, useCallback, useEffect, useRef, useReducer } from 'react'
 import { useParams, useNavigate } from 'react-router-dom'
 import {
   ReactFlowProvider,
@@ -74,6 +74,7 @@ function DiagramEditorInner() {
   const historyStack = useRef<{ nodes: Node[]; edges: Edge[] }[]>([])
   const historyIndex = useRef<number>(-1)
   const MAX_HISTORY = 50
+  const [, forceHistoryUpdate] = useReducer((x: number) => x + 1, 0)
 
   const pushHistory = useCallback((currentNodes: Node[], currentEdges: Edge[]) => {
     historyStack.current = historyStack.current.slice(0, historyIndex.current + 1)
@@ -86,7 +87,8 @@ function DiagramEditorInner() {
     } else {
       historyIndex.current += 1
     }
-  }, [])
+    forceHistoryUpdate()
+  }, [forceHistoryUpdate])
 
   const undo = useCallback(() => {
     if (historyIndex.current <= 0) return
@@ -95,7 +97,8 @@ function DiagramEditorInner() {
     setNodes(snapshot.nodes)
     setEdges(snapshot.edges)
     setIsDirty(true)
-  }, [setNodes, setEdges])
+    forceHistoryUpdate()
+  }, [setNodes, setEdges, forceHistoryUpdate])
 
   const redo = useCallback(() => {
     if (historyIndex.current >= historyStack.current.length - 1) return
@@ -104,7 +107,8 @@ function DiagramEditorInner() {
     setNodes(snapshot.nodes)
     setEdges(snapshot.edges)
     setIsDirty(true)
-  }, [setNodes, setEdges])
+    forceHistoryUpdate()
+  }, [setNodes, setEdges, forceHistoryUpdate])
 
   const canUndo = historyIndex.current > 0
   const canRedo = historyIndex.current < historyStack.current.length - 1