feat: implement Phase 2 two-tier architecture with Steward

Add comprehensive two-tier architecture where Steward analyzes requests
and Tatlock executes with scoped tools. Includes full infrastructure for
request preprocessing, tool tracking, benchmarking, and streaming.

**Added:**
- Steward agent for request analysis and capability recommendation
- Household Registry for centralized capability management
- Request preprocessing pipeline (Steward → Tatlock flow)
- Tool usage tracking and benchmarking system
- Streaming transparency (Steward reasoning visible in streams)
- Structured logging with operation timing
- Redis benchmark storage with 30-day expiry
- Benchmark analysis CLI tools

**Infrastructure:**
- src/agents/steward/ - Steward agent implementation
- src/agents/tatlock_core/ - Tatlock capability domain
- src/core/preprocessing.py - Request preprocessing pipeline
- src/core/tool_tracking.py - Tool call tracking
- src/core/benchmarks.py - Benchmark recording system
- src/core/household_registry.py - Capability registry
- src/core/startup.py - Application startup coordination
- src/core/logging_config.py - Structured logging setup

**Integration:**
- Responses API uses Steward for Tatlock requests
- Chat Completions wraps Responses API for OpenAI compatibility
- Streaming coordinator supports Steward + Tatlock flow
- Tool scoping per request based on Steward recommendations

**Testing:**
- Integration tests for Steward-Tatlock flow
- Benchmark and registry unit tests
- Steward streaming tests

See PHASE2_PLAN.md and PHASE2_COMPLETE.md for detailed documentation.

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

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

src/agents/tatlock_core/capability.py

@@ -0,0 +1,28 @@
+"""
+Household capability definition for Tatlock's core tools.
+
+Provides the executive summary that the Steward and Butler see
+for coordinating household capabilities.
+"""
+from src.core.household_registry import HouseholdCapability
+
+
+TATLOCK_CORE_CAPABILITY = HouseholdCapability(
+    name="tatlock_core",
+    role="Butler's Core Tools",
+    category="core",
+    description="Essential tools for computation, date/time operations, and web searches",
+    domains=["computation", "datetime", "information", "research"],
+    cost="low",
+    requires_network=True,  # For web search
+)
+
+
+def get_capability() -> HouseholdCapability:
+    """
+    Get the capability summary for Tatlock's core tools.
+
+    Returns:
+        HouseholdCapability executive summary
+    """
+    return TATLOCK_CORE_CAPABILITY