Function check_transaction 

pub fn check_transaction(
    tx: &Transaction,
) -> Result<ValidationResult, ConsensusError>

CheckTransaction: 𝒯𝒳 → {valid, invalid}

A transaction tx = (v, ins, outs, lt) is valid if and only if:

1. |ins| > 0 ∧ |outs| > 0
2. ∀o ∈ outs: 0 ≤ o.value ≤ M_max
3. ∑_{o ∈ outs} o.value ≤ M_max (total output sum)
4. |ins| ≤ M_max_inputs
5. |outs| ≤ M_max_outputs
6. |tx| ≤ M_max_tx_size
7. ∀i,j ∈ ins: i ≠ j ⟹ i.prevout ≠ j.prevout (no duplicate inputs)
8. If tx is coinbase: 2 ≤ |ins[0].scriptSig| ≤ 100

Uses fast-path checks before full validation.