feat(md-print): add timestamp footer option

docs/markdown.md

@@ -471,7 +471,7 @@ data-config:
 - 自动分页：内容按块级元素流入 A5 页面，段落、列表和表格可在分页处拆分
 - 每张 A4 横版放两个 A5 页面，每个 A5 页面默认两列
 - 预览中可直接打印或另存为 PDF
-- 支持页眉标题、页码和中缝裁切线
+- 支持页眉标题、页码、导出时间戳和中缝裁切线
 
 **属性：**
 
@@ -483,6 +483,7 @@ data-config:
 | `font` | number | `3` | 正文字号（毫米） |
 | `title` | string | - | 页眉标题 |
 | `pageNumbers` | boolean | `true` | 是否在页面外侧角落显示页码 |
+| `timestamp` | boolean | `false` | 是否在页码旁边显示导出时间 |
 | `cutMarks` | boolean | `true` | 是否显示 A4 中缝裁切线 |
 
 **YAML 写法：**
@@ -495,8 +496,17 @@ margin: 10
 gap: 5
 font: 3
 title: 规则书
+timestamp: true
 ```
 
+**导出时间戳：**
+
+```markdown
+:md-print[./rules.md]{timestamp=true}
+```
+
+开启后页脚会显示类似 `3 / 12 · 2026-10-23 14:05` 的内容。页码位于页面外侧底角：左侧 A5 在左下角，右侧 A5 在右下角。
+
 **打印设置：** 在浏览器打印对话框中选择 A4、横向、无边距、100% 缩放。
 
 ### 🧶 叙事线组件 (md-yarn-spinner)

docs/reference.md

@@ -48,7 +48,7 @@ Nest with more colons (`::::`, `:::::`).
 | `:md-dice` | dice formula | `key` |
 | `:md-table` | CSV path or inline id | `roll`, `remix` |
 | `:md-deck` | CSV path | `size`, `grid`, `layers` |
-| `:md-print` | markdown path, optional #section | `columns`, `margin`, `gap`, `font`, `title`, `pageNumbers`, `cutMarks` |
+| `:md-print` | markdown path, optional #section | `columns`, `margin`, `gap`, `font`, `title`, `pageNumbers`, `timestamp`, `cutMarks` |
 | `:md-link` | path, optional #section | — |
 | `:md-embed` | path, optional #section | `headingBase` |
 | `:md-bg` | image path or CSS color | `fit` |
@@ -116,15 +116,19 @@ Prefer the `yaml role=tag` form — it is the only form that supports template l
 
 Paginates a markdown document into A4 landscape sheets for printing.
 
-Each sheet holds two A5 pages side by side, and each A5 page flows the markdown into `columns` columns. `margin`, `gap`, and `font` are in millimetres (the body font defaults to 3mm). `pageNumbers` adds an `n / total` footer in the outer corner and `cutMarks` draws the centre cut line. The preview modal exports through the browser's print dialog (choose A4 landscape, no margins, 100% scale).
+Each sheet holds two A5 pages side by side, and each A5 page flows the markdown into `columns` columns. `margin`, `gap`, and `font` are in millimetres (the body font defaults to 3mm). `pageNumbers` adds an `n / total` footer in the outer corner, `timestamp` appends the export time to that footer, and `cutMarks` draws the centre cut line. The preview modal exports through the browser's print dialog (choose A4 landscape, no margins, 100% scale).
 
 - Body: markdown path, optional #section
-- Attributes: `columns`, `margin`, `gap`, `font`, `title`, `pageNumbers`, `cutMarks`
+- Attributes: `columns`, `margin`, `gap`, `font`, `title`, `pageNumbers`, `timestamp`, `cutMarks`
 
 ```markdown
 :md-print[./rules.md]{columns="2" margin="10" gap="5" font="3"}
 ```
 
+```markdown
+:md-print[./rules.md]{timestamp=true}
+```
+
 ````markdown
 ```yaml role=tag
 tag: md-print
@@ -134,6 +138,7 @@ margin: 10
 gap: 5
 font: 3
 title: 规则书
+timestamp: true
 ```
 ````