fix: resolve water rendering white-out and depth sorting issues

[braedonsaunders]

White-out fix (WaterMaterial.ts):

• Remove .mul(0.5).add(0.5) encoding from normalNode - TSL expects actual normals in [-1,1] range, not texture-encoded [0,1] values
• Remove manual fresnel/specular calculation from colorNode that was causing double-lighting with PBR pipeline
• Switch to MeshPhysicalNodeMaterial with proper IOR (1.33 for water) for physically-correct fresnel without manual calculation
• Remove unused uniforms (uFresnelPower was defined but never wired)
• Simplify quality settings to PBR-appropriate values

Depth sorting fix (UnifiedWaterMesh.ts):

• Add globalWaterLevel and useGlobalSeaLevel config options
• Track minElevation per region during flood-fill
• Use consistent water level per region instead of per-cell elevation
• Ocean biome uses global sea level, others use region minimum
• Prevents water from rendering above terrain due to elevation mismatch

Re-enable water in previously disabled biomes:

• Frozen, Void, Jungle biomes had water disabled due to "animated diagonal stripe artifacts" - same root cause
• Re-enable with appropriate water levels now that fix is in place
• Also re-enable void spores particle effect

Root causes identified:

1. normalNode returned [0,1] encoded normals instead of [-1,1] actual
2. Manual fresnel/specular in colorNode double-counted with PBR lighting
3. Per-cell elevation caused water height inconsistency within regions
4. AI-generated maps could have water cells with high elevations

https://claude.ai/code/session_01ChDF73v8WwcjKe7cWV82iB