feat(ai-outfit): 左栏新增「标题生成」(看图→提示词→AI 文字标题→写回A列) (§19.18)

AI 穿搭页左栏新增独立的「生成标题」流程：用户写标题提示词，AI 看该行
衣服图（目录行取首图）生成电商标题，逐行立即写回 Excel A 列并刷新明细表；
完成后重载 Excel，紧接「开始生成」跑图即用新标题。移除原「最终生成要求预览」
腾出版面（docs/11 §17）。

- ai_text_service.py：AiTextClient 复用图像服务 HTTP 管道做文本输出；
  chat/gemini 带图视觉，images/images_edits 明确报错；extract_text 取首条标题
- ai_title.py + TitleResult：单行编排，never raises
- excel_service.write_title_result：只写 A 列、不动 D/E/F
- config_service：title_model 默认 + load/save_title_prompt + 默认标题话术
- 面板：标题生成组（提示词+标题模型下拉+保存+生成标题）置于话术组上方；
  _TitleWorker 顺序逐行+立即回填+刷新；与「开始生成」互斥；删预览相关组件
- 测试：文本解析/payload、generate_title（单文件/目录首图/失败）、
  write_title_result、面板标题组存在且无预览；全套 py37 通过

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

src/services/config_service.py

@@ -27,12 +27,14 @@ DEFAULT_CONFIG = {
     "outfit_quality": "均衡",
     "outfit_retry_failed": False,
     "outfit_prompt_name": "默认",  # last-selected 话术模板 name (docs/11 §7.2)
+    "title_model": "",             # last-selected 标题模型 name (docs/11 §17.3)
 }
 
 _CONFIG_FILENAME = "app_config.json"
 _AI_MODELS_FILENAME = "ai_models.json"
 _OUTFIT_PROMPT_FILENAME = "outfit_prompt.txt"        # legacy single prompt (migrated)
 _OUTFIT_PROMPTS_FILENAME = "outfit_prompts.json"     # multi named templates (§7.2)
+_TITLE_PROMPT_FILENAME = "title_prompt.txt"          # single 标题生成提示词 (§17.3)
 DEFAULT_OUTFIT_PROMPT_NAME = "默认"
 
 # Default outfit prompt (docs/11 §7). Seeded into outfit_prompts.json on first run.
@@ -42,6 +44,12 @@ DEFAULT_OUTFIT_PROMPT = (
     "电商主图风格，不加文字与促销标签。"
 )
 
+# Default title prompt (docs/11 §17.3). Used by 标题生成 when title_prompt.txt absent.
+DEFAULT_TITLE_PROMPT = (
+    "请根据这件女装的款式、版型、颜色与印花特点，生成一条适合台湾蝦皮电商的中文商品标题："
+    "突出卖点与适穿场景，控制在 30 字以内。只输出标题本身一行，不要序号、引号、表情或促销词。"
+)
+
 
 def load_config():
     """
@@ -173,6 +181,34 @@ def save_outfit_prompt(text):
         logger.error("Failed to save outfit prompt to %s: %s", prompt_file, exc)
 
 
+def load_title_prompt():
+    """Return the saved 标题生成提示词, or the built-in default (docs/11 §17.3)."""
+    from services.file_service import get_config_path
+    prompt_file = get_config_path(_TITLE_PROMPT_FILENAME)
+    if not prompt_file.exists():
+        return DEFAULT_TITLE_PROMPT
+    try:
+        with open(str(prompt_file), encoding="utf-8-sig") as f:
+            text = f.read()
+        return text if text.strip() else DEFAULT_TITLE_PROMPT
+    except OSError as exc:
+        logger.warning("Title prompt unreadable (%s): %s", exc, prompt_file)
+        return DEFAULT_TITLE_PROMPT
+
+
+def save_title_prompt(text):
+    """Persist the 标题生成提示词 (utf-8, no BOM). Does not raise."""
+    from services.file_service import get_config_path
+    prompt_file = get_config_path(_TITLE_PROMPT_FILENAME)
+    try:
+        prompt_file.parent.mkdir(parents=True, exist_ok=True)
+        with open(str(prompt_file), "w", encoding="utf-8") as f:
+            f.write(text)
+        logger.info("Title prompt saved to %s", prompt_file)
+    except OSError as exc:
+        logger.error("Failed to save title prompt to %s: %s", prompt_file, exc)
+
+
 def _normalize_prompts(data):
     """Keep only valid {name, text} entries (non-empty name, string text)."""
     if not isinstance(data, list):