* feat(gameplay): add Ocean biome with water generation and heightmap adjustments
- Introduce Ocean biome enum, builder, and detection logic.
- Add ocean water building to all existing biomes and modify heightmap thresholds for low mountainous areas.
- Skip cave and river generation in Ocean (and River) biomes; avoid carving water blocks.
- Comment out border blending call and update block fill logic.
* fix(gameplay): re-enable border blending and protect water in cave gen
* refactor(generation): move ocean water build to later phase
* feat(block): add is_transitional property and refine border blending
* fix(block): set stone block as transitional
* fix(world): generate temporary chunks for surface blend neighbor data
* fix(gameplay): simplify block fill logic in blend_surface_blocks_borders
* refactor(tree): remove debug logging and unused include
