Python 2 `/` did integer division, Python 3 returns float. Changed to
`//` in zobjectparser (attribute byte offset) and zmemory (address
bounds checks). Zork 1 hit this on the first test_attr opcode.
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.
Copies the cleaned-up zvm source (ruff-compliant, ty-clean) back into
the zmachine module. Adds __init__.py with proper exports and updates
.gitignore for debug.log/disasm.log.
