refactor(schemas): remove NormalizedResponse backward-compat __init__; use canonical API

tests/test_ai_client_tool_loop_send_func.py

@@ -7,14 +7,14 @@ from __future__ import annotations
 from typing import Any
 from unittest.mock import MagicMock, patch
 from src.openai_compatible import NormalizedResponse
+from src.openai_schemas import UsageStats
 from src.ai_client import run_with_tool_loop
 from src.vendor_capabilities import VendorCapabilities
 
 def _make_normalized_response(text: str = "ok", tool_calls: list[dict[str, Any]] | None = None) -> NormalizedResponse:
  return NormalizedResponse(
   text=text, tool_calls=tool_calls or [],
-  usage_input_tokens=10, usage_output_tokens=5,
-  usage_cache_read_tokens=0, usage_cache_creation_tokens=0,
+  usage=UsageStats(input_tokens=10, output_tokens=5, cache_read_tokens=0, cache_creation_tokens=0),
   raw_response=None,
  )