feat: production multi-strat rebalance bot (lean enterprise core)
Single-file cron-ready IBKR rebalancer for the adaptive book. Money-touching core only: env config
(no secrets), paper/live guard (refuses live without MULTISTRAT_ALLOW_LIVE_CONFIRMED), leverage cap,
HWM drawdown circuit-breaker, fat-finger per-order cap, once-per-period idempotency, stale-price
guard, post-trade reconciliation, structured JSON audit log. Default dry-run; run needs
MULTISTRAT_EXECUTE=true. Verified vs cluster ib-gateway paper (DU9600528): gates pass, 6-order plan,
JSON audit trail + HWM state persisted.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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