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/core/startup.py

@@ -0,0 +1,70 @@
+"""
+Application startup module.
+
+Handles initialization of household registry and other startup tasks.
+This module should be called during application startup to register
+all household members.
+"""
+from src.agents.tatlock_core import TATLOCK_CORE_CAPABILITY, tatlock_core_tools
+from src.core.household_registry import get_household_registry
+from src.core.logging_config import get_logger
+
+logger = get_logger(__name__)
+
+
+def register_household_members():
+    """
+    Register all household members with the registry.
+
+    This function should be called during application startup to make
+    household capabilities available to the Steward.
+
+    Currently registers:
+    - tatlock_core: Butler's core tools (calculator, datetime, web search)
+
+    Future phases will add:
+    - librarian: Research and knowledge management
+    - developer: Software development assistance
+    - etc.
+    """
+    registry = get_household_registry()
+
+    logger.info("household_registration_starting")
+
+    # Register Tatlock's core tools
+    registry.register(
+        name="tatlock_core",
+        capability=TATLOCK_CORE_CAPABILITY,
+        tools=tatlock_core_tools,
+        agent=None,  # No expert agent for core tools
+    )
+
+    logger.info(
+        "household_member_registered",
+        name="tatlock_core",
+        tool_count=len(tatlock_core_tools),
+    )
+
+    logger.info(
+        "household_registration_complete",
+        total_members=len(registry),
+    )
+
+
+def initialize_application():
+    """
+    Initialize the application.
+
+    Performs all startup tasks:
+    1. Register household members
+    2. (Future) Initialize connections
+    3. (Future) Load configuration
+
+    This should be called once during application startup.
+    """
+    logger.info("application_initialization_starting")
+
+    # Register household members
+    register_household_members()
+
+    logger.info("application_initialization_complete")