Publish individual release binary assets

[wayyoungboy]

Summary

• publish each packaged command binary as an individual release asset alongside the existing per-platform archive
• add per-file checksums for the individual binary assets
• make release smoke checks verify individual assets in CI while keeping archive-only smoke behavior available by default

Validation

• bash -n scripts/build_binary_package.sh scripts/build_linux_binaries.sh
• python -m pytest tests/unit/test_release_binary_ci.py -q
• python -m black --check scripts/smoke_binary_package.py tests/unit/test_release_binary_ci.py
• git diff --check
• built a local Linux binary package and verified the generated individual assets match the archive contents and checksums

Notes

The GitHub Actions release matrix passed for Linux amd64, macOS amd64, macOS aarch64, and Windows amd64 binary jobs on this PR.

Closes #1110.

[lightzt99]

LGTM