feat(mermaid): Markdown 预览安全渲染 Mermaid 图表（strict 清洗 + 懒加载 chunk + 点击放大） (#164)

* feat(mermaid): 新增 mermaid 懒加载 chunk（构建链四处同步 + mermaid 依赖）

tsdown CHUNKS / bundle-route CHUNK_NAMES / chunk-loader ChunkName /
package.json files 同步注册 mermaid chunk；mermaid ^11.16.1 进依赖与
lockfile；chunk 构建注入 uuid 浏览器入口别名，绕开 node:crypto 纯度门。

* feat(mermaid): Markdown 预览安全渲染 mermaid 图表 + 点击放大弹窗

- splitMermaidBlocks 纯函数按 fence 切块，无 mermaid 文件零行为变化；
- mermaid.initialize 走 securityLevel strict + htmlLabels:false，不应用
  bindFunctions（静态图）；渲染 SVG 经 mermaid-sanitize 二次清洗：
  删 foreignObject/script/外来 HTML 元素、剥 @*/on* 属性、移除全部
  href/xlink:href，仅接受 SVG 根，解析失败返回空串；
- 点击图表弹出放大弹窗（滚轮缩放/拖拽平移/快捷键，借鉴 PR #75 交互，
  基于已清洗 SVG 克隆重写，不新增攻击面）；
- 深浅色跟随重渲、失败回退错误条 + 原码、CodeBlock 同款 chrome。

* test(mermaid): splitter/sanitize 单测 + chunk 清单同步 + 挂载冒烟 diagram.md

- mermaid-blocks.spec 10 例 fence 切块语义；
- mermaid-sanitize.spec 8 例 XSS（foreignObject/on*/@*/href/xlink:href/
  script/外来元素/畸形 XML/非 SVG 根）；
- bundle-route / chunk-artifact / manifest-consistency 清单加入 mermaid
  （chunk-artifact 补 addEventListener stub）；
- 挂载冒烟新增 diagram.md：client-mermaid.js 往返、SVG 节点文字、
  点击弹窗 Esc 关闭、preview 模式编辑器隐藏。

* docs(mermaid): 安全渲染设计文档 + lazy-chunks 表 + README 双语更新

设计文档记录基线决策（PR #99 架构 + PR #75 点击放大）、安全模型
（strict/htmlLabels/清洗/href 剥离/无 bindFunctions）、验证与取舍。

* fix(mermaid): sanitizer 属性名大小写归一，堵住混合大小写属性绕过（CR P1）

XML 属性名保留大小写，而输出会经 HTML 解析归一化（dangerouslySetInnerHTML），
oNload/HREF/xlink:HREF 这类混合大小写属性此前会漏过清洗。比较前先
toLowerCase()，按原名删除；新增混合大小写事件/链接属性回归用例。

* fix(mermaid): sanitizer 元素黑名单大小写归一，堵住混合大小写元素绕过（CR P1）

XML 元素名保留大小写，querySelectorAll('script') 等选择器匹配不到
<sCrIpT>/<foreignobject>，而输出经 HTML 解析会被归一化为 SVG
script/foreignObject（可执行/可注入 HTML）。改为遍历全部元素按
localName.toLowerCase() 命中小写黑名单后整节点删除；新增混合大小写
script/foreignObject/外来 HTML 元素回归用例（jsdom 实证：旧选择器
命中 0，新逻辑命中 2）。

* fix(mermaid): 单次 Markdown 解析 + 占位交换（CR P1）+ CommonMark fence 规则（CR P2）

P1（跨 fence 语义）：弃用逐块 MarkdownText 拆分，改为整篇文档单次
MarkdownText 渲染，布局后把 language-mermaid 代码块交换为 MermaidDiagram
（React 管理的 .md-code-block 宿主保留在树中、display:contents 抑制盒子，
协调安全；块不再 mermaid 时还原原 children）。新增
tests/mermaid-markdown.spec.tsx 与 e2e 跨 fence 引用链接断言。

P2（fence 匹配）：支持 3+ 反引号与波浪号开 fence；闭 fence 须同字符且
长度不小于开 fence；反引号 info string 含反引号不视为开 fence；修复
带缩进开 fence 的 info 提取。blocks 单测 +3 例。

tests/e2e/mount.e2e.ts

@@ -15,11 +15,12 @@
  *     fail() strips, no `pageerror`, no plugin-prefixed console errors);
  *  4. expands the collapsed panel (openByDefault defaults off), sweeps every
  *     built-in tab (Files / Source Control / Tasks / Terminal / Browser) —
- *     including the lazily-fetched terminal chunk — and then opens a seeded
- *     file through the Files window's tree (in-place mode: the seeded home
- *     tab itself switches to the file, no new tab), while a response wait
- *     armed before goto proves the lazily-fetched editor chunk
- *     (client-editor.js) loaded.
+ *     including the lazily-fetched terminal chunk — and then opens seeded
+ *     files through the Files window's tree (in-place mode: the seeded home
+ *     tab itself switches to the file, no new tab), while response waits
+ *     armed before goto prove the lazily-fetched editor chunk
+ *     (client-editor.js) and the mermaid chunk (client-mermaid.js, rendered
+ *     SVG diagram + zoom modal) loaded.
  *
  * Deterministic by construction: every wait is on a DOM/network marker, the
  * suite is serial (one server instance), and any crash trips the very next
@@ -42,6 +43,11 @@ const WORKSPACE_PATH = process.env.DSH_E2E_WORKSPACE ?? join(tmpdir(), 'dsh-e2e-
  *  exercise the file-open path (editor chunk = client-editor.js). */
 const SEEDED_FILE = 'hello.txt'
 
+/** A markdown file with a mermaid fence, opened through the Files window's
+ *  tree to force the lazily-packed mermaid chunk (client-mermaid.js) to load
+ *  and render a sanitized SVG diagram. */
+const SEEDED_MD_FILE = 'diagram.md'
+
 /**
  * The plugin's crash markers. The client mounts inside an error boundary that
  * renders a strip whose text starts with these prefixes instead of crashing
@@ -54,11 +60,31 @@ const BUILTIN_TABS = ['Files', 'Source Control', 'Tasks', 'Terminal', 'Browser']
 
 let api: APIRequestContext
 
-/** Seed one workspace + one session (plus a file for the editor-chunk probe)
- *  through the host's unary RPC surface. */
+/** Seed one workspace + one session (plus files for the editor/mermaid-chunk
+ *  probes) through the host's unary RPC surface. */
 async function seedSession(): Promise<void> {
   mkdirSync(WORKSPACE_PATH, { recursive: true })
   writeFileSync(join(WORKSPACE_PATH, SEEDED_FILE), 'hello from the mount lane\n')
+  // The mermaid-chunk probe file: a markdown doc whose preview must fetch
+  // client-mermaid.js and render the fence into an SVG diagram. The
+  // reference-style link's definition sits AFTER the fence: it only
+  // resolves when the preview is one single markdown parse (the mermaid
+  // path must not split the document into independent MarkdownText blocks).
+  writeFileSync(join(WORKSPACE_PATH, SEEDED_MD_FILE), [
+    '# Diagram',
+    '',
+    '[before][shared]',
+    '',
+    '```mermaid',
+    'graph TD',
+    '  A[Hello] --> B[World]',
+    '```',
+    '',
+    '[shared]: https://example.com',
+    '',
+    'tail text',
+    '',
+  ].join('\n'))
   const workspace = await api.post(`${BASE_URL}/api/workspace.create`, {
     data: { type: 'client-request', rpcId: 'e2e-workspace', method: 'workspace.create', payload: { path: WORKSPACE_PATH } },
   })
@@ -230,6 +256,54 @@ test('plugin mounts into the DSH shell and survives a built-in tab sweep', async
   await page.waitForTimeout(1_500)
   await assertNoCrash()
 
+  // The mermaid chunk (client-mermaid.js) only loads when a previewed
+  // markdown file contains a mermaid fence. Open the seeded diagram file
+  // from the files window's tree (the embedded tree stays pinned while
+  // hello.txt is open) and require the full round-trip: chunk fetch +
+  // sanitized SVG diagram in the preview, so a missing/corrupt mermaid
+  // chunk or a broken render fails the lane.
+  const mermaidChunk = page.waitForResponse(
+    (response) => response.url().includes('/sidebar/bundle/mermaid.js'),
+    { timeout: 30_000 },
+  )
+  const mdRow = sidebar.locator(`[role="button"][title$="${SEEDED_MD_FILE}"]:visible`)
+  await expect(mdRow, `the seeded "${SEEDED_MD_FILE}" file must appear in the files window's tree`).toHaveCount(1, { timeout: 30_000 })
+  await mdRow.click({ position: { x: 8, y: 8 } })
+  await mermaidChunk
+  await expect(
+    sidebar.locator('[data-mermaid-diagram] svg'),
+    'the mermaid fence must render into an SVG diagram in the markdown preview',
+  ).toHaveCount(1, { timeout: 30_000 })
+  // Labels must survive as real SVG <text> (htmlLabels stays off so the
+  // sanitizer's foreignObject strip cannot eat the node text).
+  await expect(
+    sidebar.locator('[data-mermaid-diagram]').first(),
+    'the diagram node labels must render inside the SVG',
+  ).toContainText('Hello', { timeout: 30_000 })
+  // Cross-fence semantics: the reference-style link [before][shared] must
+  // resolve to the definition that sits AFTER the fence — proof that the
+  // preview is a single markdown parse and not per-fence fragments.
+  await expect(
+    sidebar.locator('a[href="https://example.com"]').first(),
+    'reference-style links with definitions across a mermaid fence must resolve',
+  ).toContainText('before', { timeout: 30_000 })
+  // Click-to-enlarge: clicking the diagram opens the zoom modal (portalled
+  // to document.body), Esc closes it again.
+  const modal = page.locator('[data-mermaid-modal]')
+  await sidebar.locator('[data-mermaid-diagram] svg').first().click()
+  await expect(modal, 'clicking the diagram must open the zoom modal').toHaveCount(1, { timeout: 10_000 })
+  await page.keyboard.press('Escape')
+  await expect(modal, 'Esc must close the zoom modal').toHaveCount(0, { timeout: 10_000 })
+  // The preview/edit toggle is mutually exclusive: in preview mode the
+  // CodeMirror surface must be hidden (regression guard — a stale css copy
+  // in the page made the editor stay visible under the preview, breaking
+  // the toggle semantics).
+  await expect(
+    sidebar.locator('.cm-editor').first(),
+    'preview mode must hide the CodeMirror editor (mutually exclusive toggle)',
+  ).toBeHidden()
+  await assertNoCrash()
+
   // The plugin's own console prefix must never appear in errors, and no
   // unhandled rejection may escape the sweep.
   const pluginErrors = consoleErrors.filter((text) => /dsh-better-sidebar|Unhandled/.test(text))