Worldgen Phase 2: migrate existing biome points to multi-parameter scoring

[MichaelFisher1997]

Parent: #646

Phase

Phase 2: Multi-parameter biome selection

Goal

Move the existing biome set from heat/humidity Voronoi points to richer multi-parameter definitions.

Tasks

• Convert ocean, coast, lowland, wetland, forest, jungle, cold, dry, and mountain families.
• Preserve common-biome frequency where intentional.
• Revisit biome weights/priorities under the new scoring model.
• Update selector tests and baseline expectations.

Acceptance Criteria

• All existing BiomeId values remain selectable where intended.
• Rare/special biomes remain rare unless intentionally changed.
• No common biome family disappears from representative seeds.

Dependencies

• Requires multi-parameter biome point data structure.

Parallelization

Can run in parallel with ocean/coast/river priority and LOD consistency work after the selector shape is in place.

[github-actions]

Comment posted successfully to issue #651. The analysis identifies this as a well-scoped feature request for migrating the Voronoi-based biome selection from 2D (heat/humidity) to multi-parameter scoring, and outlines the key files and changes needed.

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