KOS_OP_OBJECT_INPLACE

• Style: OPCOUNT. Arg packs a KosOperand selector (high byte) with the reduce count (low byte).

• Stack: [..., a1, ..., aN] → [..., result]. In-place reduce the N operands left-to-right (values[0] is the accumulator seed) via kos_inplace_reduce (operator.c), the PyNumber_InPlace* protocol family. The consolidated replacement for the old per-operator OBJECT_INPLACE_* family.