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/steward/agent.py

@@ -8,8 +8,8 @@ This creates a two-tier architecture that prevents cognitive overload.
 Uses plain text output (not JSON) for reliability. Supports both Claude
 (preferred) and Ollama (fallback) backends via direct API calls.
 """
+
 import httpx
-from typing import Optional
 
 from src.anthropic.model_selector import get_model_info, is_claude_available, resolve_backend
 from src.core.config import config
@@ -29,9 +29,7 @@ def build_steward_prompt(query: str, conversation_history: list[dict]) -> str:
 
     cap_list = []
     for cap in capabilities:
-        cap_list.append(
-            f"• {cap.name} - {cap.description} (domains: {', '.join(cap.domains)})"
-        )
+        cap_list.append(f"• {cap.name} - {cap.description} (domains: {', '.join(cap.domains)})")
     capabilities_text = "\n".join(cap_list)
 
     # Format conversation history if present
@@ -114,7 +112,7 @@ class StewardAgent:
     def __init__(self):
         """Initialize Steward with backend selection based on availability."""
         # Ollama config (primary)
-        self.ollama_host = str(config.OLLAMA_HOST).rstrip('/')
+        self.ollama_host = str(config.OLLAMA_HOST).rstrip("/")
         self.ollama_model = config.OLLAMA_DEFAULT_MODEL
 
         # Claude config (fallback)
@@ -139,6 +137,7 @@ class StewardAgent:
         """Get or create Anthropic client (lazy initialization)."""
         if self._anthropic_client is None:
             from anthropic import AsyncAnthropic
+
             self._anthropic_client = AsyncAnthropic(api_key=config.ANTHROPIC_API_KEY)
         return self._anthropic_client
 
@@ -167,20 +166,16 @@ class StewardAgent:
                     "stream": False,
                     "options": {
                         "temperature": 0.3,  # Lower = more consistent
-                        "top_p": 0.9
-                    }
-                }
+                        "top_p": 0.9,
+                    },
+                },
             )
 
             response.raise_for_status()
             result = response.json()
             return result["response"].strip()
 
-    async def analyze(
-        self,
-        query: str,
-        conversation_history: Optional[list[dict]] = None
-    ) -> str:
+    async def analyze(self, query: str, conversation_history: list[dict] | None = None) -> str:
         """
         Analyze query and return plain text recommendation.