Function check_bip90 

pub fn check_bip90(
    block_version: i64,
    height: u64,
    activation: &impl IsForkActive,
) -> Result<bool, ConsensusError>

BIP90: Block Version Enforcement

Enforces minimum block versions based on activation heights. Mathematical specification: Orange Paper Section 5.4.4

BIP90Check: ℋ × ℕ → {valid, invalid}

Activation Heights:

• BIP34: Mainnet 227,931 (requires version >= 2)
• BIP66: Mainnet 363,725 (requires version >= 3)
• BIP65: Mainnet 388,381 (requires version >= 4)