Function emit 

pub fn emit(methods: &[StackMethod]) -> Result<EmitResult, String>

Emit a slice of StackMethods as Bitcoin Script hex and ASM.

For contracts with multiple public methods, generates a method dispatch preamble using OP_IF/OP_ELSE chains.

Note: peephole optimization (VERIFY combinations, SWAP elimination) is handled by optimize_stack_ops in optimizer.rs, which runs before emit.