Add complete Ouroboros trading system with TDD test suite

Implement the full autonomous trading agent architecture:
- KIS broker with async API, token refresh, leaky bucket rate limiter, and hash key signing
- Gemini-powered decision engine with JSON parsing and confidence threshold enforcement
- Risk manager with circuit breaker (-3% P&L) and fat finger protection (30% cap)
- Evolution engine for self-improving strategy generation via failure analysis
- 35 passing tests written TDD-first covering risk, broker, and brain modules
- CI/CD pipeline, Docker multi-stage build, and AI agent context docs

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

src/logging_config.py

@@ -0,0 +1,42 @@
+"""JSON-formatted structured logging for machine readability."""
+
+from __future__ import annotations
+
+import logging
+import sys
+from datetime import datetime, timezone
+from typing import Any
+
+import json
+
+
+class JSONFormatter(logging.Formatter):
+    """Emit log records as single-line JSON objects."""
+
+    def format(self, record: logging.LogRecord) -> str:
+        log_entry: dict[str, Any] = {
+            "timestamp": datetime.now(timezone.utc).isoformat(),
+            "level": record.levelname,
+            "logger": record.name,
+            "message": record.getMessage(),
+        }
+        if record.exc_info and record.exc_info[1]:
+            log_entry["exception"] = self.formatException(record.exc_info)
+        # Merge any extra fields attached to the record
+        for key in ("stock_code", "action", "confidence", "pnl_pct", "order_amount"):
+            value = getattr(record, key, None)
+            if value is not None:
+                log_entry[key] = value
+        return json.dumps(log_entry, ensure_ascii=False)
+
+
+def setup_logging(level: int = logging.INFO) -> None:
+    """Configure the root logger with JSON output to stdout."""
+    handler = logging.StreamHandler(sys.stdout)
+    handler.setFormatter(JSONFormatter())
+
+    root = logging.getLogger()
+    root.setLevel(level)
+    # Avoid duplicate handlers on repeated calls
+    root.handlers.clear()
+    root.addHandler(handler)