feat(provider): 重构模型测试对话框，加固 Vertex AI 传输层

模型测试:
- 将消息输入替换为完整 JSON 请求体编辑器，支持格式化和校验
- 新增端点选择面板，测试前可选择目标端点
- 新增调试检查器，可查看每次尝试的请求/响应头和体
- 结果视图改用 HorizontalRequestTimeline 组件展示请求追踪
- endpoint_checker 返回完整调试数据，通过 candidate extra_data 持久化

Vertex AI:
- 改进上下文检测逻辑，不再仅依赖 provider_type，支持从 base_url 推断
- Service Account 密钥现支持自动拉取模型（使用 auth_config 而非 api_key）
- 移除 Gemini Developer API 回退，API Key 仅走 Express 模式
- 端点表单为 Vertex AI 显示格式特定的默认路径模板
- 密钥格式校验仅在 auth_type/api_formats 变更时执行

其他:
- 禁用 ClaudeCode 提供商类型创建入口
- Dialog 组件新增 closeOnBackdrop 属性

tests/services/test_upstream_fetcher_vertex_ai_models.py

@@ -52,7 +52,7 @@ async def test_fetch_models_for_key_vertex_api_key_custom_fetcher() -> None:
 
 
 @pytest.mark.asyncio
-async def test_fetch_models_for_key_vertex_service_account_ignores_soft_404_when_success() -> None:
+async def test_fetch_models_for_key_vertex_service_account_fetches_google_and_claude() -> None:
     auth_config = {
         "project_id": "demo-project",
         "client_email": "svc@example.iam.gserviceaccount.com",
@@ -74,16 +74,27 @@ async def test_fetch_models_for_key_vertex_service_account_ignores_soft_404_when
         (
             [
                 {
-                    "id": "gemini-2.0-flash",
+                    "id": "gemini-3.1-pro-preview",
                     "owned_by": "google",
-                    "display_name": "Gemini 2.0 Flash",
+                    "display_name": "Gemini 3.1 Pro Preview",
                     "api_format": "gemini:chat",
                 }
             ],
             None,
             True,
         ),
-        ([], "HTTP 404: not found", False),
+        (
+            [
+                {
+                    "id": "claude-3-7-sonnet@20250219",
+                    "owned_by": "anthropic",
+                    "display_name": "Claude 3.7 Sonnet",
+                    "api_format": "claude:chat",
+                }
+            ],
+            None,
+            True,
+        ),
     ]
 
     with (
@@ -111,7 +122,8 @@ async def test_fetch_models_for_key_vertex_service_account_ignores_soft_404_when
     assert errors == []
     assert meta is None
     ids = {m.get("id") for m in models}
-    assert "gemini-2.0-flash" in ids
+    assert "gemini-3.1-pro-preview" in ids
+    assert "claude-3-7-sonnet@20250219" in ids
 
 
 @pytest.mark.asyncio
@@ -132,7 +144,6 @@ async def test_fetch_models_for_key_vertex_api_key_returns_soft_404_when_all_fai
             AsyncMock(
                 side_effect=[
                     ([], "HTTP 404: not found", False),
-                    ([], "HTTP 404: not found", False),
                 ]
             ),
         ),