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/toolset.py

@@ -0,0 +1,88 @@
+"""
+PydanticAI toolset for Tatlock's core tools.
+
+Converts the core tool functions into PydanticAI tool definitions
+that can be registered with agents and the household registry.
+"""
+from pydantic_ai.tools import Tool
+
+from . import tools
+
+
+# Create tool definitions for PydanticAI
+calculator_tool = Tool(
+    function=tools.calculate,
+    name="calculate",
+    description=(
+        "Safely evaluate mathematical expressions. "
+        "Supports basic arithmetic (+, -, *, /, %, **), "
+        "functions (sqrt, sin, cos, log, exp, etc.), "
+        "and constants (pi, e). "
+        "Use this for ALL mathematical calculations."
+    ),
+)
+
+current_datetime_tool = Tool(
+    function=tools.get_current_datetime,
+    name="get_current_datetime",
+    description=(
+        "Get the current date and time. "
+        "Supports various formats: 'full' (datetime), 'date' (YYYY-MM-DD), "
+        "'time' (HH:MM:SS), 'iso' (ISO 8601), or custom strftime format. "
+        "Use this instead of guessing the current date/time."
+    ),
+)
+
+time_offset_tool = Tool(
+    function=tools.calculate_time_offset,
+    name="calculate_time_offset",
+    description=(
+        "Calculate a date/time relative to now. "
+        "Accepts natural language like '1 week ago', '2 days from now', "
+        "'3 months ago', etc. "
+        "Use this for calculating past or future dates."
+    ),
+)
+
+time_difference_tool = Tool(
+    function=tools.time_difference,
+    name="time_difference",
+    description=(
+        "Calculate the difference between two dates. "
+        "Accepts dates in YYYY-MM-DD or YYYY-MM-DD HH:MM:SS format. "
+        "Second date can be 'now'. "
+        "Returns human-readable difference (e.g., '5 days, 3 hours')."
+    ),
+)
+
+web_search_tool = Tool(
+    function=tools.search_web,
+    name="search_web",
+    description=(
+        "Search the web using SearXNG for current information. "
+        "Use this to find recent events, current data, or verify facts. "
+        "Returns formatted results with titles, URLs, and snippets. "
+        "Useful for information that may have changed since training data."
+    ),
+    takes_ctx=False,
+)
+
+
+# Combined toolset of all core tools
+tatlock_core_tools = [
+    calculator_tool,
+    current_datetime_tool,
+    time_offset_tool,
+    time_difference_tool,
+    web_search_tool,
+]
+
+
+def get_core_tools():
+    """
+    Get list of Tatlock's core tool definitions.
+
+    Returns:
+        List of PydanticAI Tool objects
+    """
+    return tatlock_core_tools