- Change radiusGrowth from 1.25 to 2.0 so level N doubles the previous
level (L2 = 10240, L3 = 20480, L4 = 40960 px)
- Update all data descriptions, docs, and test defaults to match
- Add refreshHudTetherLevel() in SurfaceScene so the HUD line re-decodes
when a tether build completes while on-surface
- Rename rocky-planet-02 asset (typo fix), add 03-a/03-b variants,
point rocky frames at indices 6–8 in planets.json
- Add dev/tether-flow harness to exercise the full L2 build flow end-to-end
