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/preview-engine/tests/docx-media-runtime.test.ts

@@ -30,17 +30,32 @@ describe("DOCX 媒体捕获计划", () => {
         "img, svg"
       )
     );
+    const article = document.querySelector<HTMLElement>("#write")!;
+    article.getBoundingClientRect = () =>
+      ({
+        x: 0,
+        y: 0,
+        left: 0,
+        top: 0,
+        right: 700,
+        bottom: 900,
+        width: 700,
+        height: 900,
+        toJSON: () => ({})
+      }) as DOMRect;
+    const horizontalPositions = [0, 200, 400];
     media.forEach((element, index) => {
+      const left = horizontalPositions[index]!;
       element.getBoundingClientRect = () =>
         ({
-          x: 10,
+          x: left,
           y: 20 + index * 100,
-          left: 10,
+          left,
           top: 20 + index * 100,
-          right: 650,
-          bottom: 380 + index * 100,
-          width: 640,
-          height: 360,
+          right: left + 300,
+          bottom: 170 + index * 100,
+          width: 300,
+          height: 150,
           toJSON: () => ({})
         }) as DOMRect;
     });
@@ -52,12 +67,13 @@ describe("DOCX 媒体捕获计划", () => {
 
     expect(
       targets.map(
-        ({ id, kind, kindOrdinal, altText, caption }) => ({
+        ({ id, kind, kindOrdinal, altText, caption, alignment }) => ({
           id,
           kind,
           kindOrdinal,
           altText,
-          caption
+          caption,
+          alignment
         })
       )
     ).toEqual([
@@ -66,21 +82,24 @@ describe("DOCX 媒体捕获计划", () => {
         kind: "image",
         kindOrdinal: 1,
         altText: "架构截图",
-        caption: "系统架构"
+        caption: "系统架构",
+        alignment: "left"
       },
       {
         id: "docx-media-2",
         kind: "mermaid",
         kindOrdinal: 1,
         altText: "处理流程",
-        caption: undefined
+        caption: undefined,
+        alignment: "center"
       },
       {
         id: "docx-media-3",
         kind: "echarts",
         kindOrdinal: 1,
         altText: "年度收入",
-        caption: "收入趋势"
+        caption: "收入趋势",
+        alignment: "right"
       }
     ]);
     expect(
@@ -96,6 +115,19 @@ describe("DOCX 媒体捕获计划", () => {
       </article>
     `;
     const image = document.querySelector("img")!;
+    const article = document.querySelector<HTMLElement>("#write")!;
+    article.getBoundingClientRect = () =>
+      ({
+        x: 0,
+        y: 0,
+        left: 0,
+        top: 0,
+        right: 800,
+        bottom: 900,
+        width: 800,
+        height: 900,
+        toJSON: () => ({})
+      }) as DOMRect;
     image.getBoundingClientRect = () =>
       ({
         x: 0,
@@ -115,6 +147,8 @@ describe("DOCX 媒体捕获计划", () => {
     });
 
     expect(target?.displayWidthPx).toBeLessThanOrEqual(800);
+    expect(target?.displayHeightPx).toBeLessThanOrEqual(900);
+    expect(target?.alignment).toBe("center");
     expect(
       (target?.captureWidthPx ?? 0) *
         (target?.rasterScale ?? 0)