Backward-looking HER: on trade close, compute peak unrealized PnL
during the trade's lifetime. If peak >> actual, inject synthetic
transition with peak_pnl and boosted priority. Teaches the agent
optimal wave-exit timing 10× faster than sparse reward alone.
Two kernels: rl_hindsight_track (per-step mid accumulation) and
rl_hindsight_inject (synthetic push on done with coordination).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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