Skyveil Cloudlands Pass 7

Adds optional Cloudlands Happy Ghast population support.

Important compatibility note:
- This project is still built from the current NeoForge/Minecraft baseline used by the local mod projects.
- Happy Ghasts are looked up dynamically by entity id, defaulting to minecraft:happy_ghast.
- If the current Minecraft version/modpack does not register that entity, spawning safely skips and reports that the entity is unavailable instead of crashing.
- You can set cloudlands_happy_ghast_entity_id to a backport mod entity id if needed.

Behavior:
- Generated normal cloud islands and rain clouds try to maintain up to the configured Happy Ghast count in their center chunk.
- Default cap is 1 Happy Ghast per Cloudlands chunk.
- Happy Ghasts spawn in clear sky above cloud islands and are persistent by default.
- Manual command added: /skyveilcloudlands populate_happy_ghasts_near <radius>

Config defaults:
- enable_cloudlands_happy_ghasts = true
- cloudlands_happy_ghast_entity_id = "minecraft:happy_ghast"
- cloudlands_happy_ghasts_per_chunk = 1
- cloudlands_happy_ghast_spawn_radius = 20
- cloudlands_happy_ghast_existing_check_y_radius = 64
- cloudlands_happy_ghasts_persistent = true
