feat(frontend): M9 模态 UI（mode 系统+共享 store+WS 客户端 + chat(思维链/工具回显/情绪徽标)/code/Agent 监控/后台思考页 + Miuix 设计 token + PWA）；tsc+vite build 通过

frontend/web/src/lib/util.ts

@@ -0,0 +1,12 @@
+/** Generate a reasonably-unique id without external deps. */
+export function uid(): string {
+  if (typeof crypto !== "undefined" && "randomUUID" in crypto) {
+    return crypto.randomUUID();
+  }
+  return `id-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
+}
+
+/** Current epoch milliseconds. */
+export function now(): number {
+  return Date.now();
+}