[codex] Harden packaged install and sandbox smoke

[ravenSanstete]

Summary

• add Apache-2.0 license metadata, release docs, and PyPI-oriented install guidance
• add CI package smoke for build, twine check, wheel install, CLI benchmark checks, and clean artifact assertions
• add optional Docker sandbox smoke workflow plus a packaged Docker variant for the sandbox coding example
• make StrongReject usable from installed wheels with a packaged smoke fixture
• extend web runtime tests for bundled-source behavior and clear Node/npm preflight errors

Validation

• python -m twine check /private/tmp/snowl-package-check-hardening-3/*
• python scripts/package_smoke.py --dist-dir /private/tmp/snowl-package-check-hardening-3
• SNOWL_RUN_DOCKER_SMOKE=1 python -m pytest -q tests/test_sandbox_docker_smoke.py
• python -m pytest -q