Fee buffer and error isolation

config.py

@@ -23,6 +23,7 @@ class Config:
     # Portfolio limits
     max_positions: int = 5        # Maximum concurrent holdings
     min_order_usd: float = 15.0   # Kraken minimum is ~$10; keep a small buffer
+    taker_fee_pct: float = 0.4    # Reserve this % per order for Kraken's taker fee (actual ~0.26%)
 
     # ── Risk management ──────────────────────────────────────────────────────
     # Trailing stop: sell if price drops this % below its peak since purchase.