feat: OpenMesh 基础平台与 MD/PDF 转换技能

- 后端: coworker 智能体框架, WS API, 文件上传, 附件处理
- 前端: Open WebUI, 文件全量走 upload API (含 MD/TXT/JSON 等文本类)
- 技能: md-to-office (pandoc + wkhtmltopdf)
- 修复: 上传文件路径丢失, Agent 搜索浪费, 输出文件跑到 uploads/
- 打包: PyInstaller one-dir, 预打包 pandoc/wkhtmltopdf/chromium

surfaces/gui/e2e/composer-platform.spec.ts

@@ -0,0 +1,23 @@
+import { test, expect } from "./fixtures";
+
+// The macOS overlay layout (traffic-light insets) must never apply on Windows —
+// Windows keeps its native title bar (alignment bug, 2026-07-21). The shell injects
+// __OCW_PLATFORM__; this simulates each platform and checks the overlay class.
+test("windows platform gets no tauri-overlay layout", async ({ page }) => {
+  await page.addInitScript(() => {
+    (window as any).__TAURI__ = {}; // simulate the desktop shell
+    (window as any).__OCW_PLATFORM__ = "windows";
+  });
+  await page.goto("/");
+  await expect(page.locator("html")).toHaveAttribute("data-platform", "windows");
+  await expect(page.locator(".app.tauri-overlay")).toHaveCount(0);
+});
+
+test("macos platform keeps the overlay layout", async ({ page }) => {
+  await page.addInitScript(() => {
+    (window as any).__TAURI__ = {};
+    (window as any).__OCW_PLATFORM__ = "macos";
+  });
+  await page.goto("/");
+  await expect(page.locator(".app.tauri-overlay").first()).toBeVisible();
+});