refactor(workflow): streamline workflow settings management

- Introduced new utility functions `settingsFromWorkflowGraph` and `workflowGraphWithSettings` to encapsulate settings extraction and graph updates.
- Updated `useWorkflowEditorState` to utilize the new utility functions for improved clarity and maintainability.
- Refactored `AssistantPage` and `WorkflowCanvas` components to leverage the new settings management functions, ensuring consistent handling of workflow settings across the application.
- Removed redundant settings handling code, enhancing overall code cleanliness.

frontend/src/components/workflow/WorkflowCanvas.tsx

@@ -56,6 +56,7 @@ import {
   type WorkflowNodeType,
 } from "./specs";
 import type { WorkflowEditorProps } from "./types";
+import { workflowGraphWithSettings } from "./graph-settings";
 
 let nodeSeq = 0;
 
@@ -160,47 +161,28 @@ export function WorkflowCanvas({
   const [addPosition, setAddPosition] = useState<{ x: number; y: number } | null>(null);
   const { screenToFlowPosition } = useReactFlow();
 
-  // 回传画布状态给外部(助手 graph)。用 ref 避免把 onChange 放进依赖导致循环。
+  // 只在可持久化的画布内容真正变化时回传。React Flow 挂载时会写入节点尺寸等
+  // 内部状态，这些不属于 workflow graph，不能因此把刚加载的助手标记为未保存。
   const onChangeRef = useRef(onChange);
+  const lastSyncedGraphRef = useRef(
+    JSON.stringify(
+      workflowGraphWithSettings(
+        fromFlow(initial.nodes, initial.edges),
+        settings,
+      ),
+    ),
+  );
   useEffect(() => {
     onChangeRef.current = onChange;
   }, [onChange]);
   useEffect(() => {
-    const graph = fromFlow(nodes, edges);
-    graph.settings = {
-      globalPrompt: settings.globalPrompt,
-      defaultLlmResourceId: settings.llm ?? "",
-      defaultAsrResourceId: settings.asr ?? "",
-      defaultTtsResourceId: settings.tts ?? "",
-      visionEnabled: settings.visionEnabled,
-      visionModelResourceId: settings.visionModelResourceId,
-      toolIds: settings.toolIds,
-      knowledgeBaseId: settings.knowledgeBaseId,
-      knowledgeMode: settings.knowledgeRetrievalConfig.mode,
-      knowledgeTopN: settings.knowledgeRetrievalConfig.topN,
-      knowledgeScoreThreshold:
-        settings.knowledgeRetrievalConfig.scoreThreshold,
-      enableInterrupt: settings.allowInterrupt,
-      turnConfig: settings.turnConfig,
-    };
+    const graph = workflowGraphWithSettings(fromFlow(nodes, edges), settings);
+    const nextGraphJson = JSON.stringify(graph);
+    if (nextGraphJson === lastSyncedGraphRef.current) return;
+
+    lastSyncedGraphRef.current = nextGraphJson;
     onChangeRef.current?.(graph);
-  }, [
-    nodes,
-    edges,
-    settings.globalPrompt,
-    settings.llm,
-    settings.asr,
-    settings.tts,
-    settings.visionEnabled,
-    settings.visionModelResourceId,
-    settings.toolIds,
-    settings.knowledgeBaseId,
-    settings.knowledgeRetrievalConfig.mode,
-    settings.knowledgeRetrievalConfig.topN,
-    settings.knowledgeRetrievalConfig.scoreThreshold,
-    settings.allowInterrupt,
-    settings.turnConfig,
-  ]);
+  }, [nodes, edges, settings]);
 
   const onConnect = useCallback(
     (connection: Connection) => {