AI写作：新增素材来源选项（知识库/技能检索）

写作表单新增「素材来源」下拉：知识库（默认 web/intranet 检索）/
技能检索（用已启用技能编排检索）。用户选择后素材收集专家首次检索
据此决定检索方式。

- state 新增 material_source 通道（缺省 knowledge_base，兼容老 session）
- researcher 首次检索（无干预）时按来源决定 is_skill_search；
  PAUSE-1「启用技能检索」按钮仍独立有效
- 前端 AIWritingRequest.materialSource + 表单下拉 + hook 提交 material_source

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -29,8 +29,15 @@ const INPUT_CLASS =
 
 const DEFAULT_KEYWORD_COUNT = 1;
 const DEFAULT_AUDIENCE = '普通读者';
+const DEFAULT_MATERIAL_SOURCE: 'knowledge_base' | 'skill' = 'knowledge_base';
 const MAX_INTENT_LENGTH = 500;
 
+// 素材来源选项：知识库=素材专家默认 web/intranet 检索；技能检索=用技能编排去检索
+const MATERIAL_SOURCE_OPTIONS: Array<{ value: 'knowledge_base' | 'skill'; label: string }> = [
+  { value: 'knowledge_base', label: '知识库' },
+  { value: 'skill', label: '技能检索' },
+];
+
 const FIELD_LABEL_CLASS = 'text-[16px] font-semibold leading-none text-[#222]';
 const FIELD_TRIGGER_CLASS =
   'h-12 w-full rounded-xl border-[#e8dedd] bg-white text-sm shadow-sm';
@@ -45,6 +52,8 @@ export function AIWritingForm({
   const [audience, setAudience] = useState('普通读者');
   const [wordCountInput, setWordCountInput] = useState('800');
   const [strictMode, setStrictMode] = useState(false);
+  const [materialSource, setMaterialSource] =
+    useState<'knowledge_base' | 'skill'>(DEFAULT_MATERIAL_SOURCE);
   const [modelName, setModelName] = useState('');
   const { models, isLoading: modelsLoading } = useModels();
 
@@ -111,6 +120,7 @@ export function AIWritingForm({
       wordCountTarget: wordCount,
       keywordCount: DEFAULT_KEYWORD_COUNT,
       writingMode: hideAdvancedFields ? 'loose' : strictMode ? 'strict' : 'loose',
+      materialSource,
       modelName: selectedModel?.name || modelName || undefined,
     });
   }
@@ -178,6 +188,29 @@ export function AIWritingForm({
           </div>
         </div>
 
+        <div className="mt-4 space-y-2">
+          <label className={FIELD_LABEL_CLASS}>素材来源</label>
+          <Select
+            value={materialSource}
+            onValueChange={(v) => setMaterialSource(v as 'knowledge_base' | 'skill')}
+            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}
+                </SelectItem>
+              ))}
+            </SelectContent>
+          </Select>
+          <p className="text-xs leading-relaxed text-muted-foreground/80">
+            知识库：素材专家默认检索方式；技能检索：用已启用的技能去编排检索。
+          </p>
+        </div>
+
         <div className="mt-4 space-y-2">
           <label className={FIELD_LABEL_CLASS}>写作模型</label>
           <Select

frontend-web/src/open-canvas/hooks/useAIWritingStream.ts

@@ -747,6 +747,7 @@ export function useAIWriting() {
           word_count_target: request.wordCountTarget,
           keyword_count: Math.max(1, Math.min(10, request.keywordCount)),
           writing_mode: request.writingMode === 'strict' ? 'strict' : 'loose',
+          material_source: request.materialSource === 'skill' ? 'skill' : 'knowledge_base',
           revision_count: 0,
           max_revisions: 3,
           status: 'researching',

frontend-web/src/open-canvas/types/ai-writing.ts

@@ -228,6 +228,8 @@ export interface AIWritingRequest {
   keywordCount: number;
   /** 写作模式：strict=严格依据素材 / loose=可结合通用知识（默认 loose） */
   writingMode: 'strict' | 'loose';
+  /** 素材来源：knowledge_base=知识库（默认检索）/ skill=技能检索（默认 knowledge_base） */
+  materialSource: 'knowledge_base' | 'skill';
 }
 
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