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/steward/__init__.py

@@ -0,0 +1,18 @@
+"""
+Steward agent package.
+
+The Steward analyzes incoming requests and recommends relevant household
+capabilities, creating a two-tier architecture with the Butler.
+"""
+from .agent import StewardAgent, get_steward_agent
+from .schemas import ConversationContext, StewardRecommendation
+from .service import analyze_request, format_steward_note
+
+__all__ = [
+    "StewardAgent",
+    "get_steward_agent",
+    "ConversationContext",
+    "StewardRecommendation",
+    "analyze_request",
+    "format_steward_note",
+]