Backtester: EUR/USD support with per-pair configs and default spread

- EURUSD aliases in PAIR_ALIASES
- main() builds PlatformConfig via pair_signals.PAIR_PRODUCERS factories
  (per-pair regime weights/gates/sessions); unregistered pairs keep the
  inline construction. XAU factory is asdict-identical to inline
  (enforced by test) so XAU runs are unchanged.
- --spread default now resolves from PAIR_INFO default_spread
  (XAU $0.30, EUR 0.0001) instead of a hardcoded gold value
- EUR strategy tag: renamed EUR_PB→EUR, detected in both bullish and
  bearish reasons[0] (SELL setups mark the bearish list)

Smoke-validated: 30-day EUR M5 run produces EUR-tagged trades with
1-pip round-trip cost charged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backtest/gpu_backtest.py

@@ -48,6 +48,7 @@ if str(PROJECT_ROOT) not in sys.path:
     sys.path.insert(0, str(PROJECT_ROOT))
 
 from config import (  # noqa: E402
+    EURUSD,
     PAIR_INFO,
     PlatformConfig,
     SignalStrength,
@@ -96,6 +97,9 @@ PAIR_ALIASES = {
     "XAUUSD": XAUUSD,
     "XAU/USD": XAUUSD,
     "GOLD": XAUUSD,
+    "EURUSD": EURUSD,
+    "EUR/USD": EURUSD,
+    "EUR": EURUSD,
 }
 
 # Bar duration in seconds — used to compute "fully-closed" cutoffs so
@@ -1632,8 +1636,8 @@ def run_backtest(
             tag = "XAU_PB"
         elif "XAU STRATEGY" in first_bull:
             tag = "XAU"
-        elif "EUR STRATEGY" in first_bull:
-            tag = "EUR_PB"
+        elif "EUR STRATEGY" in first_bull or "EUR STRATEGY" in first_bear:
+            tag = "EUR"
         elif "GBP STRATEGY" in first_bull:
             tag = "GBP_PB"
 
@@ -2034,7 +2038,7 @@ def _parse_args(argv: Optional[List[str]] = None) -> argparse.Namespace:
         description="GPU-accelerated backtester for ForexBot2",
         formatter_class=argparse.ArgumentDefaultsHelpFormatter,
     )
-    p.add_argument("--pair", required=True, help="XAUUSD | XAU/USD | GOLD")
+    p.add_argument("--pair", required=True, help="XAUUSD | GOLD | EURUSD")
     p.add_argument("--days", type=int, default=180, help="Days of history (ignored if --start/--end set)")
     p.add_argument("--start", help="ISO date YYYY-MM-DD (overrides --days)")
     p.add_argument("--end", help="ISO date YYYY-MM-DD (defaults to today)")
@@ -2047,10 +2051,11 @@ def _parse_args(argv: Optional[List[str]] = None) -> argparse.Namespace:
                    help="Override TechnicalConfig.swing_sr_lookback (0 = use config default)")
     p.add_argument("--quality", default="A+,A,B,C", help="Comma-separated allowed grades")
     p.add_argument("--strategies", default="",
-                   help="Comma-separated strategy tags to include (XAU,EUR_PB,GBP_PB,GENERIC). Empty = all.")
+                   help="Comma-separated strategy tags to include (XAU,XAU_PB,EUR,GENERIC). Empty = all.")
     p.add_argument("--no-cache", action="store_true", help="Skip parquet cache (force API fetch)")
-    p.add_argument("--spread", type=float, default=0.30,
-                   help="Round-trip cost in price units per trade (XAU ~$0.30; 0 disables)")
+    p.add_argument("--spread", type=float, default=None,
+                   help="Round-trip cost in price units per trade (default: pair's "
+                        "default_spread from PAIR_INFO — XAU $0.30, EUR 0.0001; 0 disables)")
     p.add_argument("--export-csv", help="Optional path to dump per-trade CSV (incl. indicator breakdown)")
     p.add_argument("--detail", action="store_true",
                    help="Print full per-trade reasoning (indicators, signals, agreement, why entered)")
@@ -2097,6 +2102,9 @@ def main(argv: Optional[List[str]] = None) -> int:
     else:
         start = end - timedelta(days=args.days)
 
+    spread = (args.spread if args.spread is not None
+              else PAIR_INFO[pair].get("default_spread", 0.30))
+
     bt_cfg = BacktestConfig(
         pair=pair,
         start=start,
@@ -2109,14 +2117,23 @@ def main(argv: Optional[List[str]] = None) -> int:
         use_cache=not args.no_cache,
         quality_filter=[q.strip() for q in args.quality.split(",") if q.strip()],
         strategies_only=[s.strip() for s in args.strategies.split(",") if s.strip()],
-        spread=args.spread,
+        spread=spread,
     )
 
     logger.info(
         f"Backend: {'CuPy GPU' if _GPU_AVAILABLE else 'NumPy CPU fallback'} | "
-        f"Pair: {PAIR_INFO[pair]['display']} | Window: {start.date()} → {end.date()}"
+        f"Pair: {PAIR_INFO[pair]['display']} | Window: {start.date()} → {end.date()} | "
+        f"Spread: {spread}"
     )
 
+    # Per-pair tuned configs come from the pair_signals factories (regime
+    # weights, strategy gates, sessions). Unregistered pairs fall back to
+    # the inline construction.
+    from pair_signals import PAIR_PRODUCERS  # noqa: E402 (after sys.path fix)
+    factory = PAIR_PRODUCERS.get(pair)
+    if factory is not None:
+        platform_cfg = factory(primary_tf, confirm_tfs)
+    else:
         platform_cfg = PlatformConfig(
             symbol=pair,
             display_name=PAIR_INFO[pair]["display"],