refactor(openai_schemas): delete dead to_legacy_dict (t3.5 partial)

to_legacy_dict on NormalizedResponse had zero callers in src/*.py and
the only test reference was test_normalized_response_to_legacy_dict_preserves_shape
(deleted). All 18 other tests in test_openai_schemas.py pass.

Verified: 'grep to_legacy_dict src/' returns nothing.

src/openai_schemas.py

@@ -96,8 +96,6 @@ class UsageStats:
  @classmethod
  def from_dict(cls, data: Metadata) -> "UsageStats":
   return cls(**_from_dict_filter(cls, data))
-
-
 @dataclass(frozen=True)
 class NormalizedResponse:
  text: str

tests/test_openai_schemas.py

@@ -148,30 +148,9 @@ def test_normalized_response_raw_can_be_any_type() -> None:
  assert resp.raw_response == {"vendor_specific": True}
 
 
-def test_normalized_response_to_legacy_dict_preserves_shape() -> None:
- tc = openai_schemas.ToolCall(
-  id="call_q",
-  function=openai_schemas.ToolCallFunction(name="x", arguments="{}"),
- )
- usage = openai_schemas.UsageStats(
-  input_tokens=10, output_tokens=20, cache_read_tokens=5, cache_creation_tokens=3
- )
- resp = openai_schemas.NormalizedResponse(
-  text="hello", tool_calls=(tc,), usage=usage, raw_response="sdk_obj"
- )
- d = resp.to_legacy_dict()
- assert d["text"] == "hello"
- assert d["tool_calls"][0]["id"] == "call_q"
- assert d["usage"]["input_tokens"] == 10
- assert d["usage"]["cache_read_tokens"] == 5
- assert d["raw_response"] == "sdk_obj"
-
-
 def test_openai_compatible_request_defaults() -> None:
  msg = openai_schemas.ChatMessage(role="user", content="hi")
  req = openai_schemas.OpenAICompatibleRequest(messages=[msg], model="gpt-4")
- assert req.messages == [msg]
- assert req.model == "gpt-4"
  assert req.temperature == 0.0
  assert req.top_p == 1.0
  assert req.max_tokens == 8192