Rust ranked exit tie predicate

RE-835. Reproduce with python3 scripts/analyze_rust_exit_predicate.py; focused validation: cargo xtask test-group rust-exit-predicate. Machine report.

Rust matches all 168 source cases with typed signed mode classification, global-score and ranked-field selection, early gate handling and safe rank rejection. A separate scoped intermission adapter avoids rebuilding unrelated lifecycle fixtures; original runtime remains open.

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