Task 347: Cross-validate remaining comms, ephemeris, orbital_3d, and DAG functions

Status: DONE

Description

Close cross-validation gaps for physics-critical functions that are currently unvalidated:

Physics/calculation functions (medium priority):

1. comm_timeline_linear() — generates time-series of comm delays along linear trajectory (used in communications report chart)
2. arrival_position() — computes planet position at transfer arrival time (used in orbital diagrams)
3. ship_planet_light_delay() — computes delay from ship at arbitrary position to planet (used in comm analysis)
4. out_of_plane_distance() — ecliptic Z-height for transfer trajectories (exported but not independently verified)

DAG utility functions (lower priority):

1. Dag::subgraph() — predicate-based subgraph extraction (verifiable with networkx)
2. Dag::count_crossings() — edge crossing count (geometric verification)

Approach

• Export Rust function results via cross_validation_export.rs / dag_export.rs
• Write independent Python implementations in validate_supplementary.py / validate_dag.py
• Compare results at machine epsilon tolerance

Source

Gap analysis from comprehensive cross-validation coverage audit (all 396 existing checks pass).