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/src/pandoc-media.ts

@@ -11,6 +11,7 @@ import {
 
 export interface PandocMediaMapItem {
   id: string;
+  binding: string;
   path: string;
   alt_text: string;
   caption?: string;
@@ -18,6 +19,19 @@ export interface PandocMediaMapItem {
   height: string;
 }
 
+export interface PandocMediaLayoutItem {
+  id: string;
+  binding: string;
+  kind: DocxMediaKind;
+  ordinal: number;
+  altText: string;
+  alignment: PreparedDocxMedia["resources"][number]["alignment"];
+  displayWidthPx: number;
+  displayHeightPx: number;
+  widthEmu: number;
+  heightEmu: number;
+}
+
 export interface PandocMediaMap {
   image: PandocMediaMapItem[];
   mermaid: PandocMediaMapItem[];
@@ -32,8 +46,12 @@ export interface PandocMediaFile {
 export interface PreparedPandocMedia {
   map: PandocMediaMap;
   files: PandocMediaFile[];
+  layout: PandocMediaLayoutItem[];
 }
 
+export const DOCX_MEDIA_BINDING_PREFIX = "mdtp-media:";
+const EMUS_PER_CSS_PIXEL = 9_525;
+
 function pixelsToMillimeters(value: number) {
   return (value * 25.4) / DOCX_MEDIA_CSS_DPI;
 }
@@ -91,6 +109,7 @@ export function preparePandocMedia(
     echarts: []
   };
   const files: PandocMediaFile[] = [];
+  const layout: PandocMediaLayoutItem[] = [];
   const ids = new Set<string>();
   let totalBytes = 0;
   const kindCounts: Record<DocxMediaKind, number> = {
@@ -129,8 +148,10 @@ export function preparePandocMedia(
     const relativePath = `media/media-${String(
       resource.ordinal
     ).padStart(3, "0")}.png`;
+    const binding = `${DOCX_MEDIA_BINDING_PREFIX}${resource.id}`;
     map[resource.kind].push({
       id: resource.id,
+      binding,
       path: relativePath,
       alt_text: resource.altText || `${resource.kind} 图片`,
       ...(resource.caption
@@ -139,6 +160,22 @@ export function preparePandocMedia(
       width: physicalLength(resource.displayWidthPx),
       height: physicalLength(resource.displayHeightPx)
     });
+    layout.push({
+      id: resource.id,
+      binding,
+      kind: resource.kind,
+      ordinal: resource.ordinal,
+      altText: resource.altText || `${resource.kind} 图片`,
+      alignment: resource.alignment,
+      displayWidthPx: resource.displayWidthPx,
+      displayHeightPx: resource.displayHeightPx,
+      widthEmu: Math.round(
+        resource.displayWidthPx * EMUS_PER_CSS_PIXEL
+      ),
+      heightEmu: Math.round(
+        resource.displayHeightPx * EMUS_PER_CSS_PIXEL
+      )
+    });
     files.push({
       relativePath,
       content: resource.content
@@ -147,5 +184,5 @@ export function preparePandocMedia(
   if (media.totalBytes !== totalBytes) {
     throw new Error("DOCX 媒体总大小声明不一致");
   }
-  return { map, files };
+  return { map, files, layout };
 }