test(client): 用例名统一为 should_<期望>_when_<条件>（155/155）

为什么：红线第 8 条门禁立即生效，要求 Flutter 测试命名合规；此前 155 条用例名是英文自然语言
或中文描述，合规数 0/155，属存量欠账，按"先补齐再上新功能"在本批处理。

- 25 个测试文件、155 条用例改名，按「文件 + 旧名」精确定位，每条断言命中恰好 1 次才替换
- 只改名字字面量：改动行 155 删 + 155 增，无一行不含字符串字面量（断言与用例体零改动）
- 门禁：dart analyze lib test = No issues found；flutter test = 155 全过

test/drama_detail/drama_detail_logic_test.dart

@@ -42,7 +42,7 @@ Drama _detail(String id) => Drama(
 );
 
 void main() {
-  test('a list card is upgraded to the full episode list', () async {
+  test('should_upgrade_to_full_episode_list_when_detail_loads_for_list_card', () async {
     var calls = 0;
     final logic = DramaDetailLogic(
       drama: _card('signal'),
@@ -61,7 +61,7 @@ void main() {
     logic.dispose();
   });
 
-  test('a failed load keeps the card and reports the reason', () async {
+  test('should_keep_card_and_report_reason_when_load_fails', () async {
     final logic = DramaDetailLogic(
       drama: _card('signal'),
       history: FakeWatchHistory(),
@@ -79,7 +79,7 @@ void main() {
     logic.dispose();
   });
 
-  test('an already loaded detail skips the request', () async {
+  test('should_skip_request_when_detail_is_already_loaded', () async {
     var calls = 0;
     final logic = DramaDetailLogic(
       drama: _detail('signal'),