feat: 完成 DOCX R4 元素级视觉门禁

建立 Chromium、Word 与 WPS 的可编辑内容、段落几何、页眉页脚、封面、媒体和逐页视觉比较链路。

支持封面独立分节、正文页码重启、主题页边距与横向纸张，并将自然分页差异降为诊断项。

修正代码块内边距和折叠表格单元格边框映射，14 套主题生产矩阵与六组布局视觉矩阵通过。

packages/docx-theme-engine/tests/runtime.test.ts

@@ -43,6 +43,7 @@ const computed: DocxComputedStyle = {
   borderLeft: "0px none rgb(17, 17, 17)",
   width: "640px",
   maxWidth: "none",
+  minWidth: "0px",
   minHeight: "0px",
   height: "24px",
   breakBefore: "auto",
@@ -79,6 +80,10 @@ describe("DOCX 主题样式浏览器运行时", () => {
       themeCss: '#write::before { content: "</style><script>x</script>"; }'
     });
     expect(script).toContain("theme.textContent");
+    expect(script).toContain("style[property]");
+    expect(script).toContain("contentPaddingLeft");
+    expect(script).toContain("padding-left: 8px");
+    expect(script).toContain("#write pre.md-fences \\u003e code");
     expect(script).toContain("frame.remove()");
     expect(script).not.toContain("</style><script>x</script>");
   });