fix: 统一 Excel 工作簿共享存储，修复多组件互相覆盖

office.ts（内存句柄表）、office-file-extended.ts（每次重读磁盘）、
excel-common.ts（按路径独立缓存）、extended.ts（loadSheet 每次重建）
各自持有工作簿实例并整簿写回同一文件，后保存者会整体覆盖先保存者：
列宽/行高/合并被背景色冲掉、复制的 Sheet 被新建 Sheet 冲掉等。

- 新增 excel-store.ts：按路径共享同一 ExcelJS 实例，四个模块统一接入
- resolveWorkbook 返回流程变量持有的原始句柄对象，另存为改写 path
  能同步到后续节点（此前改在副本上，下游仍写旧路径）
- 另存为后以新路径重新登记实例并释放旧路径缓存
- ReadColumn 裁掉尾部空值（共享实例下触碰空行会撑大 rowCount）
- 新增 3 个共享存储回归测试（格式保持/复制Sheet保持/另存后续写）

src/main/capabilities/office-file-extended.ts

@@ -4,6 +4,7 @@ import path from "node:path";
 import { PDFDocument } from "pdf-lib";
 import { register } from "../engine/registry";
 import { RuntimeError, type CapabilityHandler } from "../engine/types";
+import { acquireWorkbook } from "./excel-store";
 
 type WorkbookSource = { workbook: ExcelJS.Workbook; filePath: string };
 
@@ -29,8 +30,7 @@ function requiredPath(candidate: unknown, label: string, nodeId: string, compone
 
 async function loadWorkbook(args: Record<string, unknown>, nodeId: string, componentId: string): Promise<WorkbookSource> {
   const filePath = requiredPath(value(args, ["workbook", "objExcel", "objExcelWorkBook", "file", "path"]), "Excel path", nodeId, componentId);
-  const workbook = new ExcelJS.Workbook();
-  await workbook.xlsx.readFile(filePath);
+  const workbook = await acquireWorkbook(filePath);
   return { workbook, filePath };
 }
 
@@ -134,11 +134,12 @@ const readColumn: CapabilityHandler = async (_ctx, node, args) => {
   const sheet = worksheetOf(source.workbook, args);
   const column = columnNumber(value(args, ["columnName", "column", "cellPos"], "A"));
   const startRow = Math.max(1, Number(value(args, ["row", "startRow"], 1)));
-  return Array.from({ length: Math.max(0, sheet.rowCount - startRow + 1) }, (_, index) => cellValue(sheet.getCell(startRow + index, column).value));
+  const values = Array.from({ length: Math.max(0, sheet.rowCount - startRow + 1) }, (_, index) => cellValue(sheet.getCell(startRow + index, column).value));
+  // 触碰过尾部空行（如定位空单元格）会撑大 rowCount，裁掉尾部空值避免误报
+  while (values.length > 0 && (values[values.length - 1] === "" || values[values.length - 1] === null || values[values.length - 1] === undefined)) values.pop();
+  return values;
 };
-register(["Excel_Cs_ReadColumn", "Excel_GetColDataNew"], readColumn);
-
-register("Excel_Cs_DeleteRow", async (_ctx, node, args) => {
+register(["Excel_Cs_ReadColumn", "Excel_GetColDataNew"], readColumn);register("Excel_Cs_DeleteRow", async (_ctx, node, args) => {
   const source = await loadWorkbook(args, node.id, node.componentId);
   const sheet = worksheetOf(source.workbook, args);
   const mode = text(args, ["mode"]);