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-engine/tests/pandoc-structure.test.ts

@@ -85,6 +85,7 @@ describe("Pandoc 语义结构投影", () => {
                 {
                   kind: "group",
                   role: "official-classification",
+                  layout: "space-between",
                   children: [
                     text("official-secrecy", "秘密"),
                     text("official-urgency", "特急")
@@ -94,6 +95,7 @@ describe("Pandoc 语义结构投影", () => {
                 {
                   kind: "group",
                   role: "official-issue-row",
+                  layout: "space-between",
                   children: [
                     text("official-number", "示例〔2026〕1号"),
                     text(
@@ -115,6 +117,7 @@ describe("Pandoc 语义结构投影", () => {
       markerSeed: "official"
     });
 
+    expect(plan.metadataPolicy.author).toBe("suppress");
     expect(plan.titlePolicy.firstBodyHeading).toBe("suppress");
     expect(plan.prefix[0]).toMatchObject({
       kind: "container",
@@ -127,6 +130,7 @@ describe("Pandoc 语义结构投影", () => {
         {
           kind: "paragraph",
           styleId: "MdOfficialClassification",
+          layout: "space-between",
           segments: ["秘密", "特急"],
           separator: "tab"
         },
@@ -138,6 +142,7 @@ describe("Pandoc 语义结构投影", () => {
         {
           kind: "paragraph",
           styleId: "MdOfficialIssueRow",
+          layout: "space-between",
           segments: ["示例〔2026〕1号", "签发人：张三"],
           separator: "tab"
         }
@@ -228,6 +233,9 @@ describe("Pandoc 语义结构投影", () => {
 
     expect(plan).toEqual({
       schemaVersion: 1,
+      metadataPolicy: {
+        author: "suppress"
+      },
       titlePolicy: {
         metadataTitle: "emit",
         firstBodyHeading: "keep"