BTC-ETH 50/50 Threshold Rebalancing Long-Only on Binance Spot (Diversification Return / Volatility Harvesting, OHLCV-Only, 3-Parameter)

Multi-instrument long-only PORTFOLIO REBALANCING strategy on BTCUSDT.BINANCE_SPOT + ETHUSDT.BINANCE_SPOT using daily bars. Refined from user-submitted seed: 'write a rebalance strategy for btc and eth.' This is a structural-portfolio mechanism, NOT a spread mean-reversion bet (which has been falsified 3+ times this session). The strategy maintains a 50/50 dollar-weight portfolio of BTC and ETH spot positions; whenever one asset's portfolio weight drifts beyond a ±5% band (i.e., either rises above 55% or falls below 45%), execute a rebalancing trade that returns both assets to 50/50. A minimum 14-day cooldown between rebalances prevents over-trading during high-volatility periods. The edge mechanism is the well-documented 'diversification return' / 'volatility harvesting' premium (Booth & Fama 1992, Bouchey-Nemtchinov-Paulsen-Stein 2012, Shannon's-Demon information-theoretic basis): when two assets have similar long-term drift but distinct short-term volatility paths, periodic rebalancing systematically takes from the recent winner and adds to the recent loser, harvesting a positive return geometrically that's invisible at the per-trade level. BTC and ETH are the ideal pair for this mechanism because: (a) they share similar structural long-term drift (both are major-cap crypto with positive secular growth), (b) they have meaningfully different short-term volatility (ETH typically ~1.3-1.5× BTC vol on daily returns), (c) their pairwise correlation is ~0.75-0.85 (high but not 1.0 — exactly the range where diversification return is meaningful), (d) both have 8+ years of continuous Binance Spot data for robust walk-forward, (e) both have massive spot liquidity (~$2B BTC, ~$500M ETH daily Binance spot volume) — zero liquidity-floor concerns. CRITICAL DISTINCTION FROM PRIOR FAILURES: this is NOT BTC-ETH spread mean-reversion (which has been falsified 3+ times). The strategy NEVER shorts either asset, NEVER computes a z-score, NEVER bets on convergence within a time window. It simply maintains constant exposure to a 2-asset portfolio. The 'buy low, sell high' emerges mechanically as a side effect of the band-based rebalancing — not as an active directional bet. The Booth & Fama (1992) result formally proves that this mechanism extracts a positive return even when the two assets have IDENTICAL expected returns (which is precisely why prior spread MR attempts failed — there's no convergence force, but there IS a rebalancing premium). Pure OHLCV — NO supplementary data dependency. 3 parameters total: target_btc_weight=0.50, rebalance_threshold=0.05, cooldown_days=14. Long-only by SPOT constraint.