Task 553: 3D viewer data test expansion

Status: DONE

Summary

Added 8 tests to orbital-3d-viewer-data.test.ts (16→24):

prepareFullRouteScene (new, 0→3)

1. Returns scene with type "full-route"
2. Includes all 5 planets
3. Transfer arcs match input count

prepareSaturnScene (new, 0→3)

1. Returns scene with type "saturn-ring"
2. Includes Saturn as primary body
3. Includes ring data

prepareUranusScene (new, 0→2)

1. Returns scene with type "uranus-approach"
2. Includes Uranus as primary body

Impact

• Stats: 4,015 TS, 531 Rust, 265 E2E (4,811 total)
• All 6 exported functions from orbital-3d-viewer-data.ts now tested