feat(ai): enforce direct image edit contract

tests/test_appconfig.py

@@ -635,6 +635,40 @@ class AppConfigTests(TempDirMixin, unittest.TestCase):
             ),
         )
 
+    def test_image_model_config_check_keeps_legacy_models_but_blocks_them_for_generation(self):
+        with self.make_temp_dir() as temp_dir:
+            models_path = os.path.join(temp_dir, "ai_models.json")
+            config = appconfig.default_ai_models_config()
+            legacy_image = config["models"][1]
+            legacy_image.update(
+                {
+                    "url": "https://legacy.example.com/v1/chat/completions",
+                    "model": "legacy-image",
+                    "api_key": "sk-legacy-secret",
+                    "api_type": "auto",
+                }
+            )
+            appconfig.save_ai_models_config(config, path=models_path)
+
+            loaded = appconfig.get_model("Nano Banana 2", path=models_path)
+            self.assertEqual("auto", loaded["api_type"])
+            result = appconfig.check_image_model_config("Nano Banana 2", path=models_path)
+            self.assertFalse(result["ok"])
+            self.assertTrue(result["check_only"])
+            self.assertIn("OpenAI 图片编辑接口", result["error"])
+            self.assertNotIn("sk-legacy-secret", result["error"])
+
+            appconfig.update_ai_model(
+                "Nano Banana 2",
+                path=models_path,
+                api_type="images_edits",
+            )
+            self.assertTrue(
+                appconfig.check_image_model_config("Nano Banana 2", path=models_path)["ok"]
+            )
+
+        self.assert_removed(temp_dir)
+
     def test_ai_model_test_uses_resolved_base_url(self):
         with self.make_temp_dir() as temp_dir:
             models_path = os.path.join(temp_dir, "ai_models.json")