- Reduce javadocs to one-liners across config/region/physics/tick/viz/plugin root
- Translate residual French comments; no behavioural change
- Tests adjusted where assertions referenced French strings
- Service GravityApplier qui toggle PhysicsValues.invertedGravity via CommandBuffer.replaceComponent
- Thread-safe tracker ConcurrentHashMap.newKeySet<UUID> pour dedup entre ticks
- Second pass O(N) pour restaurer la gravité à la sortie de région (trade-off v1 documenté)
- Pure diff static helper + hooks package-private pour tests unitaires sans runtime Hytale
- 6 tests verts (diff + tracker semantics)