feat: 知识库管理界面（入库监控 + 检索台）

桌面端「知识库」模块从占位变为可用：入库(切块/embedding/Milvus 监控) +
检索调试台(向量召回，带分数与来源)。

- mcp-go: 新工具 kb_search(返回结构化 JSON [{text,score}])；rag.Hit 加 json 标签
- gateway: POST /api/v1/kb/search → kb_search（结构化命中给检索台）
- desktop: lib/api ingestKb/searchKb；新 KbView(左 入库+监控日志 / 右 检索台命中列表
  带 Milvus 来源徽标+分数)；App 接 kb 视图；LeftNav 知识库 ready
- 验证: gateway/mcp-go build✓ + e2e PASS + 前端 build✓；真实浏览器——入库3条→监控
  '已入库3块'；语义查询'存储和搜索向量的组件'→Milvus(0.612)>Neo4j>NATS 排序正确,
  全走真实百炼 embedding(控制面下发)+Milvus

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-desktop/frontend/src/App.tsx

@@ -5,6 +5,7 @@ import { LeftNav, type ViewKey } from "./shell/LeftNav";
 import { BottomDrawer } from "./shell/BottomDrawer";
 import { StudioView } from "./studio/StudioView";
 import { MemoryView } from "./views/MemoryView";
+import { KbView } from "./views/KbView";
 import { Placeholder } from "./views/Placeholder";
 import { submitTask, streamTokens, type Identity } from "./lib/api";
 import type { TaskDsl } from "./lib/dsl";
@@ -70,6 +71,8 @@ export default function App() {
         <main className="min-w-0 flex-1 overflow-hidden">
           {view === "studio" ? (
             <StudioView onRun={onRun} phase={run.phase} />
+          ) : view === "kb" ? (
+            <KbView />
           ) : view === "memory" ? (
             <MemoryView identity={identity} />
           ) : (