fix(ai-outfit): preview sample rows ignore Excel status (§19.9)

Add excel_service.read_all_rows (every valid data row, status-independent) and
use it in _reload_sample_rows for the preview dropdown, so previewing still
works after the whole sheet is 完成. Generation still uses load_outfit_tasks.
+1 excel test (read_all_rows includes 完成/失败, skips incomplete); offscreen
all-完成 sheet now yields sample rows; full suite (12) green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_excel_service.py

@@ -96,6 +96,18 @@ class TestOutfitExcelService(unittest.TestCase):
 
         self.assertEqual(self._read_row(2), (None, "失败", "衣服图打不开"))
 
+    def test_read_all_rows_includes_done_failed_skips_incomplete(self):
+        from services.excel_service import read_all_rows
+
+        rows = read_all_rows(self.excel_path)
+
+        # rows 2(待处理) 3(完成) 4(失败) 6(待处理) — row 5 (空衣服图) skipped
+        self.assertEqual([r.row_index for r in rows], [2, 3, 4, 6])
+        by_idx = {r.row_index: r for r in rows}
+        self.assertEqual(by_idx[3].status, "完成")
+        self.assertEqual(by_idx[4].status, "失败")
+        self.assertEqual(by_idx[6].title, "  保留空格  ")  # raw text preserved
+
     def test_check_excel_writable_true_for_existing_workbook(self):
         from services.excel_service import check_excel_writable