fix(kiro): 加固 Kiro adapter 错误处理与请求构建逻辑

- 提取 request.py 统一 URL/headers/payload 构建，消除 handler_adapter_base 与 envelope 的重复逻辑
- 新增 error_enhancer 模块，分类 HTTP 状态码与连接错误，增强上游错误诊断信息
- envelope 实现 extract_error_text / on_http_status / on_connection_error，透传错误上下文到 eventstream rewriter
- KiroRequestContext 扩展错误状态字段，支持网络诊断信息传递
- provider_oauth_utils 改用 importlib 动态加载，避免 core 层对 services 的静态依赖
- idc auth_method 下跳过 profileArn，修复 usage 查询参数

Closes #247

Co-authored-by: AAEE86 <ppk0227@hotmail.com>

tests/services/test_provider_keys_quota_refresh_strategies.py

@@ -855,8 +855,6 @@ async def test_antigravity_refresher_success_resets_forbidden_flag(
 async def test_kiro_refresher_runtime_401_marks_key_invalid(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    from src.services.provider_keys.quota_refresh import kiro_refresher as module
-
     class _Banned(Exception):
         pass
 
@@ -881,7 +879,10 @@ async def test_kiro_refresher_runtime_401_marks_key_invalid(
         "src.services.proxy_node.resolver",
         {"resolve_effective_proxy": lambda provider_proxy, key_proxy: None},
     )
-    monkeypatch.setattr(module.crypto_service, "decrypt", lambda _v: "{}")
+    monkeypatch.setattr(
+        "src.services.provider_keys.quota_refresh.kiro_refresher.crypto_service.decrypt",
+        lambda _v: "{}",
+    )
 
     db = _FakeDB()
     key = SimpleNamespace(
@@ -919,8 +920,6 @@ async def test_kiro_refresher_runtime_401_marks_key_invalid(
 async def test_kiro_refresher_success_updates_metadata_and_auth_config(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    from src.services.provider_keys.quota_refresh import kiro_refresher as module
-
     class _Banned(Exception):
         pass
 
@@ -945,8 +944,14 @@ async def test_kiro_refresher_success_updates_metadata_and_auth_config(
         "src.services.proxy_node.resolver",
         {"resolve_effective_proxy": lambda provider_proxy, key_proxy: None},
     )
-    monkeypatch.setattr(module.crypto_service, "decrypt", lambda _v: json.dumps({"seed": 1}))
-    monkeypatch.setattr(module.crypto_service, "encrypt", lambda raw: f"ENC:{raw}")
+    monkeypatch.setattr(
+        "src.services.provider_keys.quota_refresh.kiro_refresher.crypto_service.decrypt",
+        lambda _v: json.dumps({"seed": 1}),
+    )
+    monkeypatch.setattr(
+        "src.services.provider_keys.quota_refresh.kiro_refresher.crypto_service.encrypt",
+        lambda raw: f"ENC:{raw}",
+    )
 
     key = SimpleNamespace(
         id="k1",