feat: ocean (#16)

* 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

src/gameplay/builders/biome_builder.cpp

@@ -39,4 +39,23 @@ void BiomeBuilder::place_grass() {
         }
     }
 }
+
+void BiomeBuilder::ocean_water_build() {
+    ChunkGenerator& chunk_generator = get_chunk_generator();
+    Chunk& chunk = chunk_generator.chunk();
+    auto& blocks = chunk.blocks();
+    const auto& heightmap = chunk.get_heightmap();
+
+    for (int x = 0; x < SIZE_X; ++x) {
+        for (int z = 0; z < SIZE_Z; ++z) {
+            int height = heightmap[x][z];
+            if (height <= SEA_LEVEL) {
+                for (int y = height; y <= SEA_LEVEL; y++) {
+                    blocks[Chunk::index(x, y, z)] = 7;
+                }
+            }
+        }
+    }
+}
+
 } // namespace Cubed