Dependency fix: exclude the broken REBOUND 4.5.0 release.
REBOUND 4.5.0 paired with ASSIST 1.2.3 has a destructor/lifetime heap-corruption
bug that crashes ASSIST during propagation; it is fixed in REBOUND 4.5.1. The
prior floor rebound>=4.4.11,<5 still permitted 4.5.0, so the dependency now
excludes it explicitly: rebound>=4.4.11,!=4.5.0,<5 (#33), with guard tests.
Full suite: 87 passed / 9 skipped (assist 1.2.3 + rebound 4.6.0).