chore: add agent environment check script

[JonesRoy3]

Adds scripts/check-agent-env.sh, a helper script that checks for Python 3, a virtual environment, requirements.txt, the .env file, and key environment variables used by the Polymarket Agents CLI.

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[!NOTE] Adds a bash script scripts/check-agent-env.sh to verify Python 3.9, venv/requirements, required .env keys, and CLI entrypoint for Polymarket Agents.

• Scripts:
  • Add scripts/check-agent-env.sh:
    • Checks Python 3.9 availability.
    • Verifies .venv and requirements.txt.
    • Validates .env presence and keys POLYGON_WALLET_PRIVATE_KEY, OPENAI_API_KEY.
    • Confirms scripts/python/cli.py exists and suggests help command.

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