refactor(KnowledgeManagement): 调整知识库详情页面文件列表展示逻辑

- 移除未使用的 Tag 组件导入
- 将文件标题列改为文件名列，并调整数据源为 sourceFileId
- 修改文件名显示逻辑，统一返回 "文件" 作为默认值
- 移除负责人列的显示
- 更新搜索框占位符文本为 "搜索文件名或内容"
- 调整文件名列宽度从 220px 增加到 260px
- 优化文件名解析逻辑，根据文件类型返回对应的预览文件名

frontend/src/pages/KnowledgeManagement/Detail/KnowledgeSetDetail.tsx

@@ -8,7 +8,6 @@ import {
   Empty,
   Modal,
   Table,
-  Tag,
   Tooltip,
 } from "antd";
 import { DeleteOutlined, DownloadOutlined, EditOutlined, EyeOutlined, PlusOutlined } from "@ant-design/icons";
@@ -148,7 +147,7 @@ const KnowledgeSetDetail = () => {
         return lastSegment;
       }
     }
-    return record.title || "文件";
+    return "文件";
   };
 
   const handlePreviewItemFile = async (record: KnowledgeItemView) => {
@@ -268,21 +267,21 @@ const KnowledgeSetDetail = () => {
 
   const itemColumns = [
     {
-      title: "标题",
-      dataIndex: "title",
-      key: "title",
+      title: "文件名",
+      dataIndex: "sourceFileId",
+      key: "sourceFileId",
       fixed: "left" as const,
-      width: 220,
+      width: 260,
       ellipsis: true,
-    },
-    {
-      title: "状态",
-      dataIndex: "status",
-      key: "status",
-      width: 120,
-      render: (status: KnowledgeItemView["status"]) => (
-        <Tag color={status?.color}>{status?.label}</Tag>
-      ),
+      render: (_: string, record: KnowledgeItemView) => {
+        if (
+          record.contentType === KnowledgeContentType.FILE ||
+          record.sourceType === KnowledgeSourceType.FILE_UPLOAD
+        ) {
+          return resolvePreviewFileName(record);
+        }
+        return record.sourceFileId || "-";
+      },
     },
     {
       title: "类型",
@@ -293,13 +292,6 @@ const KnowledgeSetDetail = () => {
         knowledgeContentTypeOptions.find((opt) => opt.value === contentType)?.label ||
         contentType,
     },
-    {
-      title: "负责人",
-      dataIndex: "owner",
-      key: "owner",
-      width: 120,
-      ellipsis: true,
-    },
     {
       title: "来源",
       dataIndex: "sourceType",
@@ -474,7 +466,7 @@ const KnowledgeSetDetail = () => {
           <SearchControls
             searchTerm={searchParams.keyword}
             onSearchChange={handleKeywordChange}
-            searchPlaceholder="搜索标题或内容"
+            searchPlaceholder="搜索文件名或内容"
             filters={[]}
             onFiltersChange={handleFiltersChange}
             onClearFilters={() => setSearchParams({ ...searchParams, filter: { type: [], status: [], tags: [] } })}