feat: add multi-parameter biome point scoring

[MichaelFisher1997]

Summary

• Extend legacy biome point data with elevation, continentalness, ruggedness, and ridge-mask centers.
• Add multi-parameter Voronoi scoring while keeping existing selector wrappers compatible.
• Cover migrated biome points with selector regression tests.

Verification

• nix develop --command zig fmt modules/world-worldgen/src/biome_registry.zig modules/world-worldgen/src/biome_selector.zig modules/world-worldgen/src/biome_selector_tests.zig modules/world-worldgen/src/biome.zig
• nix develop --command zig build test

Fixes #655

[github-actions]

📋 Summary

This PR implements Fixes #655 by extending the Voronoi biome selection system from 2D (heat/humidity) to 6D (adding elevation, continentalness, ruggedness, and ridge-mask). The BiomePoint struct gains optional elevation, continentalness, ruggedness, and ridge_mask fields with sensible derived defaults. A new selectBiomeVoronoiMultiParam function performs the full 6D distance calculation, while existing entry points remain backward-compatible wrappers. Two new regression tests verify all migrated biome points remain selectable and that continentalness separation works correctly.

The implementation is clean, well-documented, backward-compatible, and adequately tested.

📌 Review Metadata

• Reviewed Commit SHA: a0e54cfbda4d334c184165227e005e995b1efc19
• Reviewed PR: feat: add multi-parameter biome point scoring #674
• Linked Issue: Fixes Worldgen Phase 2: migrate existing biome points to multi-parameter scoring #655 — The PR fully addresses the issue by adding multi-parameter Voronoi scoring as requested.
• Overall Quality: High-quality, focused change with good test coverage.

🔴 Critical Issues (Must Fix - Blocks Merge)

None identified.

⚠️ High Priority Issues (Should Fix)

None identified.

💡 Medium Priority Issues (Nice to Fix)

None identified.

ℹ️ Low Priority Suggestions (Optional)

None identified.

📊 SOLID Principles Score

Principle	Score	Notes
Single Responsibility	9	BiomePoint gains data fields; selectors stay pure and focused.
Open/Closed	9	Extends Voronoi without modifying existing caller contracts.
Liskov Substitution	10	All existing biome points remain selectable; wrappers preserve behavior.
Interface Segregation	10	Clean separation between 2D wrapper and 6D multi-param API.
Dependency Inversion	10	Pure functions, no new dependencies, reads from existing registry.
Average	9.6

🎯 Final Assessment

Overall Confidence Score: 92%

How to interpret: 81-100%: High confidence, ready to merge or with trivial fixes

Confidence Breakdown:

• Code Quality: 95% (clean, idiomatic Zig; good docs; no allocation)
• Completeness: 90% (fully addresses Worldgen Phase 2: migrate existing biome points to multi-parameter scoring #655; good test coverage)
• Risk Level: 90% (pure functions, backward-compatible, low blast radius)
• Test Coverage: 92% (regression tests for all biome points + separation test)

Merge Readiness:

• All critical issues resolved
• SOLID average score >= 6.0
• Overall confidence >= 60%
• No security concerns
• Tests present and passing (if applicable)

Verdict:

MERGE

Clean, backward-compatible extension of Voronoi biome selection with solid regression tests.

Machine Readable Verdict

{
  "reviewed_sha": "a0e54cfbda4d334c184165227e005e995b1efc19",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 92,
  "recommendation": "MERGE"
}

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