BTC COIN-M Inverse Perp Volatility-Regime-Gated Donchian Breakout, Long-Short (Single-Instrument BTCUSD_PERP.BINANCE_CM, 4h Bars, Trade Channel Breaks ONLY in Expanding-Volatility Regime — Flat in Chop, ATR-Stopped, Pure OHLCV, 3-Parameter)

A LONG-SHORT, single-instrument directional strategy on the Binance COIN-M inverse perpetual BTCUSD_PERP.BINANCE_CM (BTC-margined, ~0.06% round-trip taker), 4-hour bars, pure OHLCV. It trades classic Donchian channel breakouts BUT gates every entry behind a volatility-regime filter: signals are taken only when the market is in an EXPANDING-volatility state, and the strategy sits flat during low-volatility chop. This is a re-attempt of a previously abandoned hypothesis whose abandon was an ENGINE BUG — a phantom COIN-M liquidation from margining a USDT-only account with qty×price maintenance margin — fixed 2026-07-24 (commit 59c8a73) to coin-funded, face-based margining; the abandoned code re-runs cleanly at 0.5× sizing, 254 trades, no liquidation, and QA credited the code. Mechanism per 4h bar: (1) compute an N-bar Donchian high/low channel (default N=30 ≈ 5 days); (2) compute a volatility-regime flag = ATR(14) is above its own rolling median over the last M bars (default M=60 ≈ 10 days) AND rising vs 6 bars ago; (3) go LONG on a close above the upper channel and SHORT on a close below the lower channel, ONLY if the vol-regime flag is TRUE — otherwise ignore all breakout signals and hold no position. It deliberately fills three under-represented buckets at once — BINANCE_CM venue (3.2% vs ≥5%), long_short direction (14.7% in a long-only-dominated book), and diversification away from the 71.5% USD-M concentration — on a low-fee venue where the fee math is forgiving. It is a single-leg CM strategy on BTC OHLCV only (L20-blessed: no multi-asset CM funding history needed), and it addresses the exact failure mode that killed the SOL 15m opening-range breakout (chop whipsaws, 28% win rate) by refusing to trade in the regime where breakouts fail-and-reverse. Against this session's trend-sleeve deaths (single-regime concentration on daily macro trend), its defense is the 4h frequency (254 trades → return stream not dominated by a handful of monster daily bars) plus a hard ATR stop and time cap so no single position rides a bull spike disproportionately.