feat: integrate tracing throughout request pipeline

Instrument the full request flow with trace spans for debugging:

- Wrap expert delegations (librarian/biographer/housekeeper) in spans
- Add orchestrate and synthesize spans to TatlockAgent
- Trace Steward analysis in preprocessing
- Start/end traces in response service with context management
- Simplify router by moving context handling to service layer
- Include tracing router in debug mode
- Remove benchmark recording from tool_tracking and steward service

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/core/preprocessing.py

@@ -11,6 +11,7 @@ from src.agents.steward import analyze_request, format_steward_note
 from src.agents.steward.schemas import StewardRecommendation
 from src.core.household_registry import get_household_registry
 from src.core.logging_config import get_logger
+from src.core.tracing import trace_span, SpanType
 
 logger = get_logger(__name__)
 
@@ -93,12 +94,32 @@ async def preprocess_request(
         conversation_id=conversation_id,
     )
 
-    # Call Steward with full conversation history
-    recommendation = await analyze_request(
-        enriched_request,
-        conversation_history=conversation_history,
-        conversation_id=conversation_id,
-    )
+    # Call Steward with full conversation history (traced)
+    async with trace_span(
+        "steward_analysis",
+        SpanType.STEWARD,
+        metadata={
+            "request_preview": user_request[:100],
+            "history_length": len(conversation_history),
+        },
+    ) as span:
+        recommendation = await analyze_request(
+            enriched_request,
+            conversation_history=conversation_history,
+            conversation_id=conversation_id,
+        )
+
+        # Update span with results
+        if span:
+            span.metadata.update({
+                "recommended_capabilities": recommendation.recommended_capabilities,
+                "complexity": recommendation.estimated_complexity,
+                "has_memory_context": bool(recommendation.memory_context),
+                "has_conversation_context": recommendation.conversation_context.has_previous_context,
+            })
+            span.details["reasoning"] = recommendation.reasoning
+            if recommendation.enriched_query:
+                span.details["enriched_query"] = recommendation.enriched_query
 
     # Format note for Tatlock (includes conversation context)
     steward_note = await format_steward_note(recommendation)