style: apply ruff's automatic fixes and formatter

Mechanical only, and separated from the judgment calls that follow so the
reviewable changes are not buried in a 98-file whitespace diff.

227 automatic fixes: 60 blank lines carrying whitespace, 60 unsorted import
blocks, 34 Optional[X] to X | None, 28 unused imports, 16 deprecated typing
imports, 12 datetime.timezone.utc to datetime.UTC, and assorted smaller
modernisations. Then `ruff format` over src and tests: 98 files reformatted,
35 already conforming.

No file among the unused-import findings defines __all__ or is an __init__.py,
so nothing here removes a re-export.

`make test`: 658 passed, unchanged from HEAD.

Two things observed while verifying, neither addressed here:

`pytest tests/` cannot collect — tests/e2e/test_orchestration_e2e.py uses an
`e2e` marker that is not registered, and the config is strict about markers.
This fails identically at HEAD, so it predates this change; `make test` passes
because it ignores tests/e2e, tests/integration and tests/contracts.

test_tatlock_tool_call_logging_calculator is flaky. It failed once in a full run
with these changes and passed on the next, passes in isolation with them, and
fails in isolation at HEAD. It is order- or timing-dependent, not a regression
from this commit — established by running the full suite both ways rather than
by reasoning about which change could have caused it.

Co-Authored-By: Claude <noreply@anthropic.com>

tests/chat/test_streaming_wrapper.py

@@ -7,7 +7,9 @@ Tests that the wrapper correctly:
 - Streams reasoning via reasoning_content field (DeepSeek R1 format)
 - Streams both reasoning and content
 """
+
 import json
+
 import pytest
 from httpx import AsyncClient
 
@@ -20,10 +22,8 @@ async def test_streaming_wrapper_enables_reasoning(async_client: AsyncClient):
     """Test that streaming wrapper automatically enables reasoning via reasoning_content."""
     request_data = {
         "model": "lorem-tester",
-        "messages": [
-            {"role": "user", "content": "Test message"}
-        ],
-        "stream": True
+        "messages": [{"role": "user", "content": "Test message"}],
+        "stream": True,
     }
 
     chunks_received = []
@@ -74,10 +74,8 @@ async def test_streaming_wrapper_reasoning_before_content(async_client: AsyncCli
     """Test that reasoning_content comes before regular content."""
     request_data = {
         "model": "lorem-tester",
-        "messages": [
-            {"role": "user", "content": "Explain something"}
-        ],
-        "stream": True
+        "messages": [{"role": "user", "content": "Explain something"}],
+        "stream": True,
     }
 
     chunk_types = []  # Track order: 'reasoning' or 'content'
@@ -127,11 +125,9 @@ async def test_streaming_wrapper_proper_chunk_structure(async_client: AsyncClien
     """Test that streaming chunks have proper structure."""
     request_data = {
         "model": "lorem-tester",
-        "messages": [
-            {"role": "user", "content": "Hello"}
-        ],
+        "messages": [{"role": "user", "content": "Hello"}],
         "temperature": 0.8,
-        "stream": True
+        "stream": True,
     }
 
     first_chunk = None
@@ -201,9 +197,9 @@ async def test_streaming_wrapper_with_system_message(async_client: AsyncClient):
         "model": "lorem-tester",
         "messages": [
             {"role": "system", "content": "You are a helpful assistant."},
-            {"role": "user", "content": "Hello"}
+            {"role": "user", "content": "Hello"},
         ],
-        "stream": True
+        "stream": True,
     }
 
     chunks_received = []
@@ -243,10 +239,8 @@ async def test_streaming_wrapper_pipeline_prefix(async_client: AsyncClient):
     """Test streaming with pipeline prefix in model name."""
     request_data = {
         "model": "some_pipeline.lorem-tester",
-        "messages": [
-            {"role": "user", "content": "Test"}
-        ],
-        "stream": True
+        "messages": [{"role": "user", "content": "Test"}],
+        "stream": True,
     }
 
     chunks_received = []
@@ -285,17 +279,11 @@ async def test_streaming_wrapper_non_streaming_fallback(async_client: AsyncClien
     """Test that non-streaming request works through wrapper."""
     request_data = {
         "model": "lorem-tester",
-        "messages": [
-            {"role": "user", "content": "Hello"}
-        ],
-        "stream": False  # Non-streaming
+        "messages": [{"role": "user", "content": "Hello"}],
+        "stream": False,  # Non-streaming
     }
 
-    response = await async_client.post(
-        "/v1/chat/completions",
-        json=request_data,
-        timeout=20.0
-    )
+    response = await async_client.post("/v1/chat/completions", json=request_data, timeout=20.0)
 
     assert response.status_code == 200
     data = response.json()