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.
write_word() was routing all header writes through game_set_header()
which enforced overly strict per-byte permissions. Zork 1 legitimately
writes to header address 2 on startup. Now uses the same dynamic/static
boundary check that viola does, matching the reference implementation.
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.
