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/biographer/agent.py

@@ -7,7 +7,8 @@ A PydanticAI agent that serves as the household's memory keeper:
 - Manages user profile and preferences
 - Forgets information when requested
 """
-from typing import Any, Optional
+
+from typing import Any
 
 from pydantic_ai import Agent
 
@@ -19,7 +20,6 @@ from src.agents.biographer.tools import (
     update_preference,
     update_profile,
 )
-from src.core.config import config
 from src.core.logging_config import get_logger
 
 logger = get_logger(__name__)
@@ -97,7 +97,7 @@ When recalling:
 """
 
 # Lazy initialization to avoid connection issues during imports
-_biographer_agent: Optional[Agent[None, str]] = None
+_biographer_agent: Agent[None, str] | None = None
 
 
 def _create_biographer_agent() -> Agent[None, str]:
@@ -126,6 +126,7 @@ def _create_biographer_agent() -> Agent[None, str]:
     agent.tool_plain(forget_memory)
 
     from src.anthropic.model_selector import get_model_info
+
     model_info = get_model_info()
     logger.info(
         "biographer_agent_created",
@@ -153,7 +154,7 @@ def get_biographer_agent() -> Agent[None, str]:
 async def run_biographer(
     task: str,
     context: str = "",
-    message_history: Optional[list[Any]] = None,
+    message_history: list[Any] | None = None,
 ) -> str:
     """
     Execute a memory task with The Biographer.
@@ -216,7 +217,7 @@ async def run_biographer(
 async def run_biographer_stream(
     task: str,
     context: str = "",
-    message_history: Optional[list[Any]] = None,
+    message_history: list[Any] | None = None,
 ):
     """
     Execute a memory task with streaming output.