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/core/tests/export-config.test.ts

@@ -27,8 +27,23 @@ describe("导出配置", () => {
       A3: { width: 297, height: 420 },
       A4: { width: 210, height: 297 },
       A5: { width: 148, height: 210 },
-      Letter: { width: 216, height: 279 },
-      Legal: { width: 216, height: 356 }
+      Letter: { width: 215.9, height: 279.4 },
+      Legal: { width: 215.9, height: 355.6 }
+    });
+  });
+
+  it("保持英制纸张的标准尺寸精度", () => {
+    expect(getPaperDimensionsMm("Letter", "portrait")).toEqual({
+      width: 215.9,
+      height: 279.4
+    });
+    expect(getPaperDimensionsMm("Letter", "landscape")).toEqual({
+      width: 279.4,
+      height: 215.9
+    });
+    expect(getPaperDimensionsMm("Legal", "portrait")).toEqual({
+      width: 215.9,
+      height: 355.6
     });
   });
 
@@ -51,7 +66,8 @@ describe("导出配置", () => {
 
   it("提供可由主题推荐的页眉和页码配置", () => {
     expect(defaultExportConfig.header).toMatchObject({
-      fontFamily: '"Segoe UI", "Microsoft YaHei", sans-serif'
+      fontFamily: '"Segoe UI", "Microsoft YaHei", sans-serif',
+      showOnFirstPage: true
     });
     expect(defaultExportConfig.footer).toMatchObject({
       fontFamily: '"Segoe UI", "Microsoft YaHei", sans-serif',
@@ -65,7 +81,8 @@ describe("导出配置", () => {
       pageDecorationsMode: undefined,
       header: {
         ...defaultExportConfig.header,
-        fontFamily: undefined
+        fontFamily: undefined,
+        showOnFirstPage: undefined
       },
       footer: {
         ...defaultExportConfig.footer,
@@ -76,10 +93,29 @@ describe("导出配置", () => {
 
     expect(parsedLegacyV4.pageDecorationsMode).toBe("theme");
     expect(parsedLegacyV4.header.fontFamily).toContain("Microsoft YaHei");
+    expect(parsedLegacyV4.header.showOnFirstPage).toBe(true);
     expect(parsedLegacyV4.footer.fontFamily).toContain("Microsoft YaHei");
     expect(parsedLegacyV4.footer.showOnFirstPage).toBe(true);
   });
 
+  it("允许页眉和页码独立控制正文首页可见性", () => {
+    const parsed = exportConfigSchema.parse({
+      ...defaultExportConfig,
+      header: {
+        ...defaultExportConfig.header,
+        enabled: true,
+        showOnFirstPage: false
+      },
+      footer: {
+        ...defaultExportConfig.footer,
+        showOnFirstPage: true
+      }
+    });
+
+    expect(parsed.header.showOnFirstPage).toBe(false);
+    expect(parsed.footer.showOnFirstPage).toBe(true);
+  });
+
   it("支持公文页码格式和奇偶页外侧对齐", () => {
     expect(
       exportConfigSchema.safeParse({