feat(settings): clarify custom gateway format

tests/test_gui.py

@@ -3139,6 +3139,12 @@ class GuiTests(TempDirMixin, unittest.TestCase):
 
             self.assertIsInstance(tab.gateway_default_button, QRadioButton)
             self.assertIsInstance(tab.gateway_custom_button, QRadioButton)
+            self.assertEqual("默认网关", tab.gateway_default_button.text())
+            self.assertEqual(
+                "自定义网关（仅支持 OpenAI 格式）",
+                tab.gateway_custom_button.text(),
+            )
+            self.assertIn("OpenAI 格式", tab.gateway_custom_button.toolTip())
             self.assertEqual(0, tab.gateway_selector.layout().spacing())
             self.assertEqual(2, tab.gateway_selector.layout().count())
             self.assertTrue(tab.gateway_default_button.isChecked())
@@ -3146,6 +3152,7 @@ class GuiTests(TempDirMixin, unittest.TestCase):
             self.assertFalse(tab.cmhub_panel.isHidden())
             self.assertTrue(tab.model_picker_panel.isHidden())
             self.assertTrue(tab.model_detail_panel.isHidden())
+            self.assertTrue(tab.custom_gateway_hint_label.isHidden())
             self.assertNotIn(
                 "模型详情",
                 [label.text() for label in tab.findChildren(QLabel)],
@@ -3164,6 +3171,11 @@ class GuiTests(TempDirMixin, unittest.TestCase):
             self.assertTrue(tab.cmhub_panel.isHidden())
             self.assertFalse(tab.model_picker_panel.isHidden())
             self.assertFalse(tab.model_detail_panel.isHidden())
+            self.assertFalse(tab.custom_gateway_hint_label.isHidden())
+            self.assertEqual(
+                "只有服务商明确说明“支持 OpenAI 格式接口”时才选择此项。",
+                tab.custom_gateway_hint_label.text(),
+            )
             self.assertFalse(tab.direct_role_panel.isHidden())
             picker_index = tab.settings_panel_layout.indexOf(tab.model_picker_panel)
             detail_index = tab.settings_panel_layout.indexOf(tab.model_detail_panel)