KOS_OP_NILP

• Style: NOARG.

• Stack: [..., x] → [..., bool]. Pop TOS; push True when it is an empty-list singleton (nil or bracket-nil), else False.

• Compiler form: Compiler.compress lowers NILP followed by JUMP_FALSE into one CHECK_NIL.

• Implementation: koskari/lib/opcode/NILP.c