feat: add Python integrity verification with SHA-256

[sigelabriana-sketch]

/claim #4

Summary

Implemented Python integrity verification for the Javelin Project.

What was added

Created anti_cheat.py with the following features:

1. SHA-256 computation: Computes hash of the running script file using Python's built-in hashlib

2. Environment variable check: Compares the computed hash against JAVELIN_EXPECTED_SHA256 env var

3. Graceful handling:

   • If JAVELIN_EXPECTED_SHA256 is not set → skips check (like C++ with JAVELIN_EXPECTED_CRC32=0)
   • If hash matches → passes, exits with code 0
   • If hash mismatch → fails, exits with code 1

Usage

# Set expected hash
export JAVELIN_EXPECTED_SHA256="$(python3 anti_cheat.py --compute)"

# Run with integrity check
python3 anti_cheat.py