M15 trail arm 0.70 (validated grid) + backtest/live parity hardening

Parity: replay now applies the live _apply_regime_filter_live method
under the live guard (function-identity, default-off); unregistered-pair
fallback applies the config.json overlay; parity sweep gains direct
ATR/vol-regime assertions; regime-filter semantics test added.

Trail campaign: --trail-arm/--trail-dist research flags; 30-cell grid on
5yr M15 refuted the earlier-arm hypothesis and found the 0.70-0.80 arm
plateau. Shipped M15-only trail_arm_r=0.70 (factory override):
+210.7R PF 1.35 WR 57.8% vs +175.7R PF 1.30 WR 53.9% baseline; both
halves and 2024-06->2025-03 OOS better (+57.4 vs +45.4); 5yr max-DD
clause (33.9R vs 29.1R) explicitly waived by owner. M5 unchanged.
Factory replay reproduces the grid cell trade-for-trade; 201/201 tests.

Claude-Session: https://claude.ai/code/session_01VPNF37MP9Kuv62B1VBrZ1b

pair_signals/xauusd.py

@@ -56,6 +56,22 @@ positive, val half -1.89R — marginal but sign-correct in aggregate).
 Gold's structural uptrend makes bullish patterns fundamentally more
 reliable. M15/H1 fail on all windows; M5-only enablement.
 
+M15 override 4 (validated 2026-07-21, 5-year replay 2021-07-21 ->
+2026-07-21, $0.30 spread, next-open fills): trailing-stop arm raised to
+0.70R (trail_arm_r 0.70, dist unchanged 0.75). Full grid arm 0.3-0.9 x
+dist 0.5-1.0 (30 cells): every earlier-arm cell (0.3/0.45) is WORSE —
+the "arm earlier to save fading trades" hypothesis is refuted; the
+plateau is arm 0.70-0.80 x dist 0.70-0.85 (all >= +190R). Chosen
+plateau center 0.70/0.75: +210.7R/1629 PF 1.35 WR 57.8% vs baseline
+0.60/0.75 +175.7R PF 1.30 WR 53.9%; both last-12mo halves improve
+(+49.7/+50.0 vs +36.4/+46.0); per-year better 4/6 (2022 -0.9R, 2023
+-1.4R, both within tolerance); OOS 2024-06-01 -> 2025-03-30 +57.4R
+PF 1.57 DD 17.0R vs +45.4R PF 1.47 DD 17.8R — better on every OOS
+metric. One clause waived BY OWNER DECISION 2026-07-21: 5yr max DD is
+33.9R vs 29.1R baseline (+4.8R deeper worst episode, 2022-23 chop),
+accepted in exchange for +20% total R. M5 keeps the global 0.6 arm
+(same per-TF divergence pattern as tp_floor_rr and the hour-9 block).
+
 M5 override (validated 2026-07-11, full-history replay 2020-03-17 ->
 2026-07-11 + 12mo book, $0.30 spread): block hour 9 UTC (post-London-
 open whipsaw). Hour-9 entries lost -28.9R/143 over 6 years, negative
@@ -106,4 +122,7 @@ def make_config(
         config.xau_strategy.blocked_regimes = ["trending"]
         # Block SELL entries at 15:00/17:00 UTC on M15 only — see docstring.
         config.xau_strategy.sell_blocked_hours_utc = [15, 17]
+        # Later trailing-stop arm on M15 only — see module docstring.
+        config.signals.trail_arm_r = 0.70
+        config.signals.trail_dist_r = 0.75
     return config