Add baseline anti-cheat monitor

[attaboy11]

Closes #2
Also addresses #4

/claim #2
/claim #4

Summary

• adds the missing Python anti-cheat monitor with debugger detection, suspicious-process detection, and optional JAVELIN_EXPECTED_SHA256 self-integrity verification
• keeps the C++ client buildable outside Windows while retaining Windows debugger/process guards
• fixes the broken C++ integrity failure path by replacing the invalid 0xCRC return literal with a real portable exit code
• documents C++/Python run paths, optional integrity setup, and exit codes
• includes a short visual demo GIF under docs/

Demo

Validation

• python3 -m unittest discover -s tests -> 12 tests passed
• python3 -m py_compile anti_cheat.py -> passed
• c++ -std=c++17 -Wall -Wextra -pedantic AntiCheat.cpp -o /tmp/javelin-anticheat-check -> passed
• /tmp/javelin-anticheat-check -> prints All clear. Continue. and exits 0
• identify docs/javelin-anticheat-demo.gif -> 4-frame 980x430 GIF verified
• git diff --check -> passed

Demo transcript

$ /tmp/javelin-anticheat-check
[Javelin AntiCheat] starting checks...
[Javelin AntiCheat] All clear. Continue.

The tests also cover debugger failure, suspicious-process failure, Python SHA-256 integrity mismatch, C++ CRC integrity mismatch, and the all-clear path for the Python monitor.