Three follow-ups from cluster smoke gp74n (trade_vol pearl validation):
1. Max-hold force-close: max_hold_ns added as per-backtest config
(default 0 = disabled). Fires force-flat (3, 0) when current_ts -
entry_ts >= max_hold_ns, BEFORE SL/trail check. Tested via
max_hold_forces_close. Sweep YAML sets 60s cap to bound the long
tail observed in gp74n (263985s pathological hold).
2. exit_px defensive sanity check: 500/1024 gp74n trades reported
exit_px = ±i32::MAX/100 (float→int saturation sentinel from likely
NaN segment_realized). Defensive fix in pnl_track_step: if exit_px
is non-finite or diverges from entry_px by >10%, fall back to
entry_px with zero realised_pnl. Root cause to be traced separately.
3. Spec §9.2 criteria revision: mean_hold<30s replaced with p95<600s
+ max<=max_hold_ns. The 30s threshold reflected the pre-pearl
sub-cost churning bug, not a real feature criterion. p95 catches
long-tail pathology while letting alpha-driven exit timing breathe.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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