fix: align LOD biome selection with registry scoring

[MichaelFisher1997]

Summary

• Route simplified LOD biome selection through the registry scoring path so it uses elevation, continentalness, ruggedness, and ridge mask like LOD0 where structural filters are unavailable.
• Add selector tests for LOD-compatible consistency and non-heat/humidity terrain signals.
• Update the BiomeSource simplified selector fixture to use a valid deep-ocean elevation.

Verification

• nix develop --command zig fmt modules/world-worldgen/src/biome_selector.zig modules/world-worldgen/src/biome_selector_tests.zig src/worldgen_tests.zig
• nix develop --command zig build test -- --test-filter selectBiomeSimple
• nix develop --command zig build test

Fixes #657

[github-actions]

📋 Summary

This PR addresses #657 (Worldgen Phase 2: keep LOD biome selection consistent with LOD0). It replaces the hardcoded, simplified selectBiomeSimple logic with a delegation to the full registry scoring path (selectBiome), ensuring LOD2+ terrain uses the same climate, elevation, continentalness, ruggedness, and ridge signals as LOD0. It also adds targeted tests for LOD-compatible consistency and updates an existing test fixture to use valid deep-ocean elevation parameters. All tests pass, code is properly formatted, and the implementation fully satisfies the issue requirements.

📌 Review Metadata

• Reviewed Commit SHA: e79d96708f2a555759b7f106c3bb9f613efe14d0
• Reviewed PR: fix: align LOD biome selection with registry scoring #673
• Linked Issue: Worldgen Phase 2: keep LOD biome selection consistent with LOD0 #657 — Implementation fully satisfies acceptance criteria: LOD uses same core climate/terrain signals as LOD0, no discontinuities introduced, and existing LOD tests pass.

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🔴 Critical Issues (Must Fix - Blocks Merge)

None identified.

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⚠️ High Priority Issues (Should Fix)

None identified.

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💡 Medium Priority Issues (Nice to Fix)

None identified.

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ℹ️ Low Priority Suggestions (Optional)

[LOW] src/worldgen_tests.zig:984 — expectEqual argument order inconsistency
Confidence: High
Description: The PR fixed the expectEqual argument order on line 995 (expectEqual(expected, actual)), but the adjacent assertion on line 984 (try testing.expectEqual(result1, BiomeId.desert)) still uses the reversed (actual, expected) convention.
Impact: Confusing error messages if the test ever fails; minor style inconsistency in the same test block.
Suggested Fix: Swap to try testing.expectEqual(BiomeId.desert, result1); for consistency.

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📊 SOLID Principles Score

Principle	Score	Notes
Single Responsibility	9	Eliminates duplicated biome selection logic; LOD now delegates to the single climate-scoring source of truth
Open/Closed	9	New biomes added to the registry automatically work in LOD without modifying selectBiomeSimple
Liskov Substitution	8	Not heavily applicable (no inheritance), but function contract is preserved
Interface Segregation	8	Signature unchanged; consumers see no API breakage
Dependency Inversion	9	Now depends on registry abstraction instead of hardcoded constants
Average	8.6

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🎯 Final Assessment

Overall Confidence Score: 95%

• Code Quality: 95% (clean deletion of 43-line duplicate, correct delegation, well-documented)
• Completeness: 95% (fulfills issue Worldgen Phase 2: keep LOD biome selection consistent with LOD0 #657 requirements, adds appropriate tests, fixes fixture)
• Risk Level: 5% (behavioral change is intentional and verified; no memory/threading/GPU concerns)
• Test Coverage: 90% (good targeted tests; could add more boundary cases but not required)

Merge Readiness:

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

Verdict:

MERGE

Clean, well-tested fix that eliminates duplicated logic and aligns LOD biome selection with the full registry path as intended.

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  "reviewed_sha": "e79d96708f2a555759b7f106c3bb9f613efe14d0",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 95,
  "recommendation": "MERGE"
}

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