feat: 完成T-204旧字段回写

实现 Excel 旧标题与旧封面路径回写原文件，按 source_file_abs/source_sheet/source_row 定位行，支持输出列自动追加、xlsm 保留 VBA、文件占用中文错误提示与 export_copy 另存副本。

Tab① 增加回写旧数据按钮与 WriteBackWorker，后台调用 excel.write_back，锁文件时提示关闭后重试；补充 Excel 与 GUI 单测覆盖回写、锁文件、另存副本和 worker 调用。

同步 harness 文档：T-204 标记完成，新增 T-204b 记录采集完成自动回写缺口，扩展 T-205 覆盖 Chrome 未启动/未登录引导保护，并更新 current-state、routes、api、architecture、requirements 与 progress。

tests/test_excel.py

@@ -1,10 +1,11 @@
 import os
 import unittest
+from unittest import mock
 
 from _helpers import TempDirMixin
 
 try:
-    from openpyxl import Workbook
+    from openpyxl import Workbook, load_workbook
 except ModuleNotFoundError:
     raise unittest.SkipTest("openpyxl 未安装")
 
@@ -23,6 +24,32 @@ class ExcelImportTests(TempDirMixin, unittest.TestCase):
         workbook.save(path)
         workbook.close()
 
+    def row_values_by_header(self, path, row_number=2):
+        workbook = load_workbook(path, data_only=True)
+        try:
+            sheet = workbook.active
+            headers = {
+                sheet.cell(row=1, column=column).value: column
+                for column in range(1, sheet.max_column + 1)
+            }
+            return {
+                header: sheet.cell(row=row_number, column=column).value
+                for header, column in headers.items()
+            }
+        finally:
+            workbook.close()
+
+    def headers(self, path):
+        workbook = load_workbook(path, data_only=True)
+        try:
+            sheet = workbook.active
+            return [
+                sheet.cell(row=1, column=column).value
+                for column in range(1, sheet.max_column + 1)
+            ]
+        finally:
+            workbook.close()
+
     def test_import_tasks_parses_rows_and_writes_batch_tasks(self):
         with self.make_temp_dir() as temp_dir:
             db_path = os.path.join(temp_dir, "cmshopee.db")
@@ -162,6 +189,104 @@ class ExcelImportTests(TempDirMixin, unittest.TestCase):
             excel.match_summary(rows, accounts),
         )
 
+    def test_write_back_writes_old_fields_to_original_excel(self):
+        with self.make_temp_dir() as temp_dir:
+            db_path = os.path.join(temp_dir, "cmshopee.db")
+            excel_path = os.path.join(temp_dir, "input.xlsx")
+            self.save_workbook(
+                excel_path,
+                [
+                    (
+                        "待处理任务",
+                        [
+                            ["账号名", "别名", "商品id"],
+                            ["主店", "alias-a", "51100639510"],
+                        ],
+                    )
+                ],
+            )
+            result = excel.import_tasks([excel_path], path=db_path)
+            task = db.list_tasks(batch_id=result["batch_id"], path=db_path)[0]
+            db.set_collected(
+                task.id,
+                "原始商品标题",
+                r"D:\images\51100639510_old.jpg",
+                path=db_path,
+            )
+
+            summary = excel.write_back(result["batch_id"], path=db_path)
+
+            self.assertEqual(True, summary["ok"])
+            self.assertEqual(1, summary["files"])
+            self.assertEqual(1, summary["rows"])
+            self.assertEqual([os.path.abspath(excel_path)], summary["written_files"])
+            values = self.row_values_by_header(excel_path)
+            self.assertEqual("原始商品标题", values["旧标题"])
+            self.assertEqual(r"D:\images\51100639510_old.jpg", values["旧封面图片路径"])
+
+        self.assert_removed(temp_dir)
+
+    def test_write_back_locked_file_raises_clear_error(self):
+        with self.make_temp_dir() as temp_dir:
+            db_path = os.path.join(temp_dir, "cmshopee.db")
+            excel_path = os.path.join(temp_dir, "input.xlsx")
+            self.save_workbook(
+                excel_path,
+                [
+                    (
+                        "待处理任务",
+                        [
+                            ["账号名", "别名", "商品id"],
+                            ["主店", "alias-a", "51100639510"],
+                        ],
+                    )
+                ],
+            )
+            result = excel.import_tasks([excel_path], path=db_path)
+            task = db.list_tasks(batch_id=result["batch_id"], path=db_path)[0]
+            db.set_collected(task.id, "原始商品标题", "old.jpg", path=db_path)
+
+            with mock.patch("app.excel.load_workbook", side_effect=PermissionError("locked")):
+                with self.assertRaisesRegex(excel.ExcelError, "Excel 文件被占用"):
+                    excel.write_back(result["batch_id"], path=db_path)
+
+        self.assert_removed(temp_dir)
+
+    def test_export_copy_writes_copy_without_touching_original(self):
+        with self.make_temp_dir() as temp_dir:
+            db_path = os.path.join(temp_dir, "cmshopee.db")
+            excel_path = os.path.join(temp_dir, "input.xlsx")
+            out_dir = os.path.join(temp_dir, "out")
+            self.save_workbook(
+                excel_path,
+                [
+                    (
+                        "待处理任务",
+                        [
+                            ["账号名", "别名", "商品id"],
+                            ["主店", "alias-a", "51100639510"],
+                        ],
+                    )
+                ],
+            )
+            result = excel.import_tasks([excel_path], path=db_path)
+            task = db.list_tasks(batch_id=result["batch_id"], path=db_path)[0]
+            db.set_collected(task.id, "原始商品标题", "old.jpg", path=db_path)
+
+            summary = excel.export_copy(result["batch_id"], out_dir, path=db_path)
+
+            self.assertEqual(1, summary["files"])
+            self.assertEqual(1, summary["rows"])
+            copy_path = summary["written_files"][0]
+            self.assertTrue(os.path.exists(copy_path))
+            self.assertIn("input_cmshopee回写", os.path.basename(copy_path))
+            self.assertNotIn("旧标题", self.headers(excel_path))
+            values = self.row_values_by_header(copy_path)
+            self.assertEqual("原始商品标题", values["旧标题"])
+            self.assertEqual("old.jpg", values["旧封面图片路径"])
+
+        self.assert_removed(temp_dir)
+
 
 if __name__ == "__main__":
     unittest.main()

tests/test_gui.py

@@ -24,6 +24,7 @@ from app.gui import (
     MainWindow,
     TAB_STYLE,
     TAB_TITLES,
+    WriteBackWorker,
 )
 
 
@@ -57,6 +58,10 @@ class GuiTests(TempDirMixin, unittest.TestCase):
             self.assertIn("padding: 8px 18px", window.tabs.styleSheet())
             self.assertIn("margin-right: 8px", window.tabs.styleSheet())
             self.assertIsInstance(window.tabs.widget(0), CollectTab)
+            self.assertEqual(
+                "回写旧数据到 Excel",
+                window.tabs.widget(0).write_back_button.text(),
+            )
 
         self.assert_removed(temp_dir)
 
@@ -382,6 +387,20 @@ class GuiTests(TempDirMixin, unittest.TestCase):
 
         self.assert_removed(temp_dir)
 
+    def test_write_back_worker_calls_excel_write_back(self):
+        with mock.patch(
+            "app.gui.excel.write_back",
+            return_value={"ok": True, "batch_id": "batch-1", "files": 1, "rows": 2},
+        ) as write_back:
+            summary = WriteBackWorker("batch-1", db_path="db.sqlite").execute()
+
+        self.assertEqual({"ok": True, "batch_id": "batch-1", "files": 1, "rows": 2}, summary)
+        write_back.assert_called_once_with(
+            "batch-1",
+            excel_path=None,
+            path="db.sqlite",
+        )
+
 
 if __name__ == "__main__":
     unittest.main()