SCU6.0: Tai-Chi Entropy Tax and Unit Pair Lifecycle — From Resource Quota to Pair Vitality with Polarization-Governed Dual-Signature Callbacks

SCU6.0 introduces the Tai-Chi Entropy Tax model and Unit Pair lifecycle ecosystem, fundamentally redefining entropy tax from a resource-quota mechanism to a pair-vitality system implementing Yin-Yang dialectical constraints. The core breakthrough repositions entropy tax as a capability-boundary limitation rather than a runtime-capacity limitation, with conservation of Yin-diminishment and Yang-growth, measured by a polarization metric bias in [-1, 1]. When polarization reaches extremes (|bias| >= 0.7), the system triggers mandatory dual-signature callbacks, forcing the Yin (critical, DeepSeek-Chat) and Yang (supportive, Qwen-Plus) perspectives to re-examine and synthesize via a Tai-Chi fusion step. The callback cost function C(b) = k * (exp(alpha * |b| / (1 - |b|)) - 1) ensures that intervention cost grows super-linearly as polarization approaches the boundary. The release introduces PairEcosystem for managing multiple specialized pairs with cross-collaboration, potential lending, and experience inheritance. A natural-death mechanism handles callback failures through experience recovery and rebirth cycles. Intent-based taxation (Scheme B) charges operations according to their polarity—Yin operations draw from the Yin energy pool, Yang operations from the Yang pool. Stability thresholds (gamma_yin >= 0.75, gamma_yang >= 0.65) govern pair renewal decisions.