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/files-explorer.spec.ts

@@ -0,0 +1,27 @@
+// UX-037: Files — an explorer over the session's roots. Each root opens in the artifact
+// viewer (breadcrumb "Files"), whose folder listings click through to subfolders and
+// files. Artifacts stays the curated scratch-only surface beside it.
+import { expect } from "@playwright/test";
+import { test } from "./fixtures";
+
+test("Files lists the session roots and browses into a file", async ({ page }) => {
+  await page.goto("/");
+  await page.getByPlaceholder(/Ask the coworker/).fill("hello");
+  await page.getByRole("button", { name: "Send" }).click();
+  await expect(page.getByText(/Echo: hello/)).toBeVisible();
+
+  // Collapsed by default like every section (the More fold is gone — owner 2026-08-20).
+  await page.getByTestId("rail-toggle-files").click();
+  const row = page.getByTestId("files-root-row").first();
+  await expect(row).toContainText("scratch");
+  await expect(row).toContainText("read-write");
+
+  // Root → folder listing in the viewer, breadcrumb says Files.
+  await row.click();
+  await expect(page.getByTestId("artifact-folder")).toBeVisible();
+  await expect(page.locator(".artifact-title")).toContainText("Files");
+
+  // Drill into a file: the same viewer renders it.
+  await page.getByRole("button", { name: /notes\.md/ }).click();
+  await expect(page.locator(".artifact-md")).toContainText("hello from the explorer");
+});