v0.5.0

Next release after v0.4.6, consolidating the former v0.4.7 scope: Rust 1.99.0 minimum, stable vector angles, correctness-preserving interval/certified/rational performance improvements, a bounded opt-in algebraic floating-point evaluation (#250), research-repo-tools v0.1.9 adoption, and verified automated crates.io publishing. Existing floating-point APIs stay strict. Expanded const-generics work is unscheduled and does not gate this release.