fix: 修正 markdown-to-jsx 导入方式 + 新增 formatDateLabel 日期工具函数

- TextPart: default import → named import
- MaterialCard: 使用 formatDateLabel 显示今天/昨天/日期
- 清理旧测试文件，新增 ResourceTable 测试

tests/web/components/chat/MarkdownTable.test.tsx

@@ -1,43 +0,0 @@
-import { screen } from "@testing-library/react";
-import { describe, expect, test } from "bun:test";
-import { createElement } from "react";
-
-import { MarkdownTable } from "../../../../src/web/features/chat/parts/MarkdownTable";
-import { renderWithProviders } from "../../test-utils";
-
-describe("MarkdownTable 渲染表格", () => {
-  test("渲染原生 table 元素并添加 class", () => {
-    const children = createElement(
-      "thead",
-      null,
-      createElement("tr", null, createElement("th", null, "列1"), createElement("th", null, "列2")),
-    );
-
-    renderWithProviders(createElement(MarkdownTable, { children }));
-
-    const table = document.querySelector(".markdown-table");
-    expect(table).toBeTruthy();
-    expect(table!.tagName).toBe("TABLE");
-    expect(screen.getByText("列1")).toBeTruthy();
-    expect(screen.getByText("列2")).toBeTruthy();
-  });
-
-  test("正确传递 children 内容", () => {
-    const children = createElement(
-      "tbody",
-      null,
-      createElement("tr", null, createElement("td", null, "值1"), createElement("td", null, "值2")),
-    );
-
-    renderWithProviders(createElement(MarkdownTable, { children }));
-
-    expect(screen.getByText("值1")).toBeTruthy();
-    expect(screen.getByText("值2")).toBeTruthy();
-  });
-
-  test("只有传入 table 元素时才有 class", () => {
-    const { container } = renderWithProviders(createElement(MarkdownTable, { children: null }));
-
-    expect(container.querySelector(".markdown-table")).toBeTruthy();
-  });
-});