feat: tune hot dry biome terrain

[MichaelFisher1997]

Summary

• Tune hot/dry biome terrain modifiers for desert, savanna, savanna plateau, windswept savanna, and badlands variants.
• Add registry coverage for the intended hot/dry relief and smoothing relationships.

Verification

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

Fixes #653

[github-actions]

📋 Summary

This PR addresses #653 ("Worldgen Phase 1: tune dry biome terrain modifiers") by tuning terrain modifiers for seven hot/dry biomes and adding test coverage to verify distinct relief profiles. The implementation aligns with the issue's acceptance criteria.

📌 Review Metadata

• Reviewed Commit SHA: 9ed3f0fa5bcf2d861d51ca57d42f28feb31dfd40
• Reviewed PR: feat: tune hot dry biome terrain #667
• Linked Issue: Worldgen Phase 1: tune dry biome terrain modifiers #653 - Fully addressed. Terrain modifiers tuned for all specified biomes, tests added to capture distribution changes.

This PR adds .terrain fields where missing and adjusts existing parameters for desert, savanna, savanna_plateau, windswept_savanna, badlands, wooded_badlands, and eroded_badlands. A comprehensive unit test verifies the intended relief relationships.

🔴 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	10	Focused solely on hot/dry biome terrain tuning
Open/Closed	9	Extends registry without modifying unrelated biomes
Liskov Substitution	10	No inheritance issues in data-driven registry
Interface Segregation	10	No interfaces involved; simple struct fields
Dependency Inversion	10	No new dependencies introduced
Average	9.8

🎯 Final Assessment

Overall Confidence Score: 95%

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

Confidence Breakdown:

• Code Quality: 95% (clean, minimal changes following existing patterns)
• Completeness: 95% (all specified biomes tuned, tests cover intended relationships)
• Risk Level: 95% (low risk - only data changes in biome registry)
• Test Coverage: 95% (new test validates all key terrain relationships)

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, focused PR that fully addresses #653 with verified tests and no concerns.

{
  "reviewed_sha": "9ed3f0fa5bcf2d861d51ca57d42f28feb31dfd40",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 95,
  "recommendation": "MERGE"
}

opencode session  |  github run