op_verify now performs actual checksum validation against the header
instead of raising NotImplemented. ZLexer is injected into ZCpu and
sread tokenizes input into the parse buffer per the V3 spec.
Implements op_print_addr, op_print_num, op_ret, and op_show_status following
TDD approach with tests first. Each opcode now properly decodes/prints text,
handles signed numbers, returns from routines, or acts as a no-op as appropriate.
Implemented 10 opcodes for object tree manipulation: get_sibling,
test_attr, set_attr, clear_attr, jin, remove_obj, print_obj,
get_prop_addr, get_next_prop, and get_prop_len.
Added 6 supporting methods to ZObjectParser: set_attribute,
clear_attribute, remove_object, get_property_data_address,
get_next_property, and get_property_length.
Fixed bug in insert_object where sibling chain walk never advanced
the prev pointer, potentially causing infinite loops.
Added 16 unit tests with MockObjectParser to verify CPU opcode
behavior. All tests passing.