fix(notebook): default material source to notebook when studioToken or initialNotebookId is set

Replace useEffect-based approach with synchronous effectiveMaterialSource
derived value to avoid first-render flash and timing issues.

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

frontend-web/src/open-canvas/components/ai-writing/AIWritingForm.tsx

@@ -97,13 +97,10 @@ export function AIWritingForm({
     [models, modelName],
   );
 
-  // initialNotebookId 存在时自动切换素材来源为「我的笔记」
-  useEffect(() => {
-    if (initialNotebookId != null) {
-      setMaterialSource('notebook');
-    }
-  // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, []);
+  // studioToken / initialNotebookId 存在时强制使用「我的笔记」
+  const effectiveMaterialSource: MaterialSource = studioToken ?? initialNotebookId != null
+    ? 'notebook'
+    : materialSource;
 
   // 初始化时加载文章类型
   useEffect(() => {
@@ -172,11 +169,11 @@ export function AIWritingForm({
       wordCountTarget: wordCount,
       keywordCount: DEFAULT_KEYWORD_COUNT,
       writingMode: hideAdvancedFields ? 'loose' : strictMode ? 'strict' : 'loose',
-      materialSource,
+      materialSource: effectiveMaterialSource,
       modelName: selectedModel?.name || modelName || undefined,
       // 只有选了"我的笔记"才传笔记参数
-      noteSearchSpaceId: materialSource === 'notebook' ? (selectedNotebookId ?? undefined) : undefined,
-      noteSourceIds: materialSource === 'notebook' && selectedNotebookId != null ? selectedDocumentIds : undefined,
+      noteSearchSpaceId: effectiveMaterialSource === 'notebook' ? (selectedNotebookId ?? undefined) : undefined,
+      noteSourceIds: effectiveMaterialSource === 'notebook' && selectedNotebookId != null ? selectedDocumentIds : undefined,
     });
   }
 
@@ -284,33 +281,26 @@ export function AIWritingForm({
 
         <div className="mt-4 space-y-2">
           <label className={FIELD_LABEL_CLASS}>素材来源</label>
-          {/* studioToken 模式：素材来源已锁定为「我的笔记」，不可切换 */}
-          {studioToken ? (
-            <div className={`${FIELD_TRIGGER_CLASS} flex items-center px-3 border rounded-xl bg-white text-sm text-muted-foreground`}>
-              我的笔记
-            </div>
-          ) : (
-            <Select
-              value={materialSource}
-              onValueChange={(v) => handleMaterialSourceChange(v as MaterialSource)}
-              disabled={disabled}
-            >
-              <SelectTrigger className={FIELD_TRIGGER_CLASS}>
-                <SelectValue placeholder="选择素材来源" />
-              </SelectTrigger>
-              <SelectContent>
-                {MATERIAL_SOURCE_OPTIONS.map((opt) => (
-                  <SelectItem key={opt.value} value={opt.value} className="text-sm">
-                    {opt.label}
-                    <span className="ml-1 text-xs text-muted-foreground">— {opt.desc}</span>
-                  </SelectItem>
-                ))}
-              </SelectContent>
-            </Select>
-          )}
+          <Select
+            value={effectiveMaterialSource}
+            onValueChange={(v) => handleMaterialSourceChange(v as MaterialSource)}
+            disabled={disabled}
+          >
+            <SelectTrigger className={FIELD_TRIGGER_CLASS}>
+              <SelectValue placeholder="选择素材来源" />
+            </SelectTrigger>
+            <SelectContent>
+              {MATERIAL_SOURCE_OPTIONS.map((opt) => (
+                <SelectItem key={opt.value} value={opt.value} className="text-sm">
+                  {opt.label}
+                  <span className="ml-1 text-xs text-muted-foreground">— {opt.desc}</span>
+                </SelectItem>
+              ))}
+            </SelectContent>
+          </Select>
 
           {/* 选了"我的笔记"才展示笔记本 / 文档选择器 */}
-          {materialSource === 'notebook' && (
+          {effectiveMaterialSource === 'notebook' && (
             <div className="mt-2 space-y-2">
               {/* studioToken 模式：笔记本已锁定，不展示选择器 */}
               {!studioToken && (