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>

src/agents/housekeeper/agent.py

@@ -8,7 +8,8 @@ the core-api service, which wraps Home Assistant REST API, offering:
 - Script execution
 - Automation management
 """
-from typing import Any, Optional
+
+from typing import Any
 
 from pydantic_ai import Agent
 
@@ -27,7 +28,6 @@ from src.agents.housekeeper.tools import (
     turn_off,
     turn_on,
 )
-from src.core.config import config
 from src.core.logging_config import get_logger
 
 logger = get_logger(__name__)
@@ -98,7 +98,7 @@ After completing actions, briefly confirm:
 """
 
 # Lazy initialization to avoid connection issues during imports
-_housekeeper_agent: Optional[Agent[None, str]] = None
+_housekeeper_agent: Agent[None, str] | None = None
 
 
 def _create_housekeeper_agent() -> Agent[None, str]:
@@ -140,6 +140,7 @@ def _create_housekeeper_agent() -> Agent[None, str]:
     agent.tool_plain(get_history)
 
     from src.anthropic.model_selector import get_model_info
+
     model_info = get_model_info()
     logger.info(
         "housekeeper_agent_created",
@@ -167,7 +168,7 @@ def get_housekeeper_agent() -> Agent[None, str]:
 async def run_housekeeper(
     task: str,
     context: str = "",
-    message_history: Optional[list[Any]] = None,
+    message_history: list[Any] | None = None,
 ) -> str:
     """
     Execute a home automation task with The Housekeeper.
@@ -234,7 +235,7 @@ async def run_housekeeper(
 async def run_housekeeper_stream(
     task: str,
     context: str = "",
-    message_history: Optional[list[Any]] = None,
+    message_history: list[Any] | None = None,
 ):
     """
     Execute a home automation task with streaming output.