KOS_OP_BUILD_LIST_EXTEND_CONST

• Style: CONST. Arg = constant pool index of a sequence (typically a pooled constant tuple).

• Stack: [..., list] → [..., list]. Extend the TOS list in place from the pooled sequence (tuple fast path, general-iterable fallback). TypeError when TOS is not a list.

• Compiler form: compile/#list tail constant run of length ≥ 2.