feat(ai): enforce direct image edit contract

app/appconfig.py

@@ -142,10 +142,10 @@ DEFAULT_AI_MODELS_CONFIG = {
             "name": "Nano Banana 2",
             "category": "image",
             "enabled": True,
-            "url": "https://api.vectorengine.ai/v1/chat/completions",
+            "url": "https://api.vectorengine.ai/v1",
             "model": "gemini-3.1-flash-image-preview",
             "api_key": "",
-            "api_type": "auto",
+            "api_type": "images_edits",
             "connect_timeout_seconds": 30,
             "timeout_seconds": 0,
             "extra_body": {},
@@ -1018,6 +1018,56 @@ def get_model(name, path=AI_MODELS_PATH) -> dict:
     return copy.deepcopy(models[_model_index(models, name)])
 
 
+def is_image_edit_model(model) -> bool:
+    """Return whether a model satisfies the direct image-edit contract."""
+
+    return (
+        isinstance(model, dict)
+        and model.get("category") == "image"
+        and model.get("api_type") == "images_edits"
+    )
+
+
+def image_model_config_error(model) -> str:
+    """Return a Chinese actionable error for a direct image model, if any."""
+
+    if not isinstance(model, dict) or model.get("category") != "image":
+        return "当前模型不是图片模型"
+    if model.get("api_type") != "images_edits":
+        return "图片模型仅支持 OpenAI 图片编辑接口，请在设置中选择该接口类型"
+    missing = [
+        field
+        for field in ("url", "model", "api_key")
+        if not str(model.get(field, "") or "").strip()
+    ]
+    if missing:
+        return "图片模型缺少必要配置：" + "、".join(missing)
+    url = str(model.get("url") or "").strip()
+    parts = urllib.parse.urlsplit(url)
+    if parts.scheme not in {"http", "https"} or not parts.netloc:
+        return "图片模型网址必须使用 http 或 https"
+    try:
+        connect_timeout = int(model.get("connect_timeout_seconds", 0) or 0)
+    except (TypeError, ValueError):
+        connect_timeout = 0
+    if connect_timeout <= 0:
+        return "图片模型连接超时必须大于 0 秒"
+    return ""
+
+
+def check_image_model_config(name, path=AI_MODELS_PATH) -> dict:
+    """Validate one image model locally without making a billable request."""
+
+    try:
+        model = get_model(name, path=path)
+        error = image_model_config_error(model)
+        if error:
+            return {"ok": False, "check_only": True, "error": error}
+        return {"ok": True, "check_only": True}
+    except Exception as exc:
+        return {"ok": False, "check_only": True, "error": str(exc)}
+
+
 
 def model_request_url(model) -> str:
     """Return the HTTP endpoint used for a configured AI model."""