Restore CI compatibility gates

[rsasaki0109]

What changed

• apply workspace-wide rustfmt output required by the Rustfmt gate
• resolve current stable Clippy errors in camera, scene, distribute, Arrow, and AI tests
• add explicit legacy DLPack export/import ownership support for NumPy 1.x while retaining versioned DLPack for NumPy 2.x
• cover the legacy zero-copy tensor path and accept both protocol versions in Python tests

Root cause

Main accumulated formatting drift and new stable-Clippy lints. Python 3.8 resolves to NumPy 1.x, whose DLPack protocol uses the legacy dltensor capsule and does not accept max_version; the binding previously emitted and required only dltensor_versioned.

Validation

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo clippy --workspace --all-features --lib -- -D warnings
• RUSTFLAGS="-D warnings" cargo test --workspace --all-features --no-run
• RUSTFLAGS="-D warnings" cargo bench --workspace --no-run
• cargo test -p spatialrust-tensor --features dlpack
• Python binding tests with NumPy 1.26.4: 81 passed, 1 skipped