fix: use workflow token for public snapshot access

[Pigbibi]

Summary

• keep dedicated snapshot and organization sync tokens as optional overrides
• fall back to the current workflow token for public cross-repo artifact access
• pass the same non-empty token into the reusable snapshot checkout

Validation

• PYTHONPATH=src:../QuantPlatformKit/src python3 -m pytest -q tests/test_drift_workflow_config.py
• actionlint .github/workflows/drift-check.yml
• git diff --check

[github-actions]

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