Rust entity class-hash search

RE-855. Reproduce with python3 scripts/analyze_rust_entity_hash.py; focused validation: cargo xtask test-group rust-entity-hash. Machine report.

Rust matches 80 original class-hash search cases, including inactive/null class filtering, collisions, nonzero signed active values and cursors beyond the scan count. Bounded safe entity slices reject invalid cursors/counts; class text is intentionally not compared because the source does not compare it.

Original executable/native runtime and complete Linux/macOS Rust/Bevy/Solari acceptance remain unverified.