KOS_OP_PUSH_WITH

• Style: CONST. Arg = constant pool index of binding name (symbol/string) or sentinel for no binding.

• Stack before: [..., mgr]. Stack after: body runs in a fresh operand segment.

• Behaviour: Pop mgr; resolve and cache enter/exit; call enter (auto-await if needed); on success bind enter result if name given; push new segment; look up WITH extent at current PC, compute resume_pc = ext->pop_pc + 1; push KOS_DYN_WITH with resume_pc stored on the node. On enter failure, no node or block is installed; exception propagates.

• Pushes: KOS_DYN_WITH (single-shot: exits once on unwind or transfer, never re-entered). Node stores resume_pc (instruction after POP_WITH) for use when exit swallows an exception.

• Invariants: Node owns one operand segment; stack restoration is structural (segment pop), not height-mark. A WITH extent must exist at the PUSH_WITH PC; otherwise RuntimeError.