KOS_OP_CDR

• Style: COUNT. Arg = repeat count: apply cdr that many times to the stack top (each step pops one pair and pushes its cdr).

• Invariants: n ≥ 1. n ≤ 0 (including CDR 0) is invalid: RuntimeError (CDR invoked with invalid argument count: …); the stack is not modified because the handler returns before popping TOS.

• Stack: With valid n ≥ 1, same effect as n chained CDR 1 instructions (one stack pop, local walk, one push). If any intermediate value is not a pair or is nil, TypeError (message includes step index and type / nil).