Task 430: Extract and Test 3D Coordinate Transform Functions

Status: DONE

Summary

Extract equatorialToEcliptic, saturnRingPlaneNormal, and uranusSpinAxis from orbital-3d-analysis.ts into a separate coordinate-transforms.ts module and add comprehensive tests. These are pure math functions with IAU-verifiable outputs but currently have zero test coverage because the parent module has a bare main() call preventing import.

Rationale

• Pure math functions ideal for TDD — verifiable against IAU J2000 constants
• Currently untested because parent module executes on import
• Coordinate transforms are foundational to 3D orbital analysis accuracy