Task 450: WASM Bridge Tests for Remaining 12 Functions

Status: DONE

Summary

Final batch of WASM test coverage. Add tests for: DAG functions (dag_analyze, dag_downstream, dag_find_paths, dag_impact, dag_layout, dag_subgraph, dag_upstream), propagation variants (propagate_adaptive_ballistic, propagate_adaptive_brachistochrone, propagate_symplectic_ballistic), mass_compute_timeline, and saturn_ring_crossing. This brings WASM test coverage to 100% of exported functions.