Skyveil Cloudlands Pass 0 scaffold.

Implemented:
- Standalone NeoForge project.
- skyveilcloudlands:soft_cloud, dense_cloud, thin_cloud, mist_cloud.
- 2.0 block jump factor on solid cloud blocks for an early Terraria-like sky movement feel.
- Cloud block fall safety behavior hooks.
- Config placeholders for high-altitude cloud island generation.

Not active yet:
- Overworld high-altitude cloud island generation.
- Mobs, structures, portals, villages, dimension logic.

Next pass should add a bounded worldgen hook or configured feature after build validation.
