fix: retune biome transition boundaries

[MichaelFisher1997]

Summary

• Expands biome transition rules for missed harsh boundaries across badlands, savanna variants, forests, taiga, and peak/lowland pairs.
• Aligns transition band width metadata with the 12-block edge detection radius.
• Adds tests for required transition categories and verifies transition micro-biomes remain edge-injected only.

Verification

• nix develop --command zig fmt modules/world-worldgen/src/biome_edge_detector.zig src/worldgen_tests.zig
• nix develop --command zig build test

Fixes #658

[github-actions]

📋 Summary

Linked Issue: Fixes #658 - "Worldgen Phase 3: retune biome adjacency and transition bands"

Issue Verification: The PR fully satisfies all requirements from #658:

• ✅ Reviews and expands TRANSITION_RULES for missing harsh boundaries (badlands variants, savanna variants, peak/lowland pairs, old_growth_taiga)
• ✅ Tunes EDGE_WIDTH from 8 to 12, aligning with the 12-block edge detection radius
• ✅ Ensures harsh boundaries get buffer biomes via expanded rule coverage
• ✅ Adds tests for important transition pairs and verifies edge-injection-only constraint
• ✅ Acceptance criteria met: desert/forest, cold/temperate, mountain/lowland, wetland/forest, ocean/coast transitions are all covered

This PR expands biome transition rules from ~47 to 83 rules, corrects a metadata constant mismatch, and adds valuable safety tests ensuring transition micro-biomes cannot spawn naturally.

📌 Review Metadata

• Reviewed Commit SHA: bfaa05172539aae494802fc60a00170a604b0543
• Reviewed PR: fix: retune biome transition boundaries #675

🔴 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	9/10	Module focused solely on edge detection and transition rules
Open/Closed	7/10	Adding rules requires modifying the array; lookup functions are stable
Liskov Substitution	8/10	Enum/struct usage is consistent across the codebase
Interface Segregation	9/10	Clean minimal API (needsTransition, getTransitionBiome)
Dependency Inversion	8/10	Reasonably coupled to BiomeId from registry
Average	8.2

🎯 Final Assessment

Overall Confidence Score: 90%

Confidence Breakdown:

• Code Quality: 90% (clean, well-organized data changes)
• Completeness: 95% (fully addresses issue Worldgen Phase 3: retune biome adjacency and transition bands #658 requirements)
• Risk Level: 10% (data-only changes, no runtime logic modified)
• Test Coverage: 90% (good tests for new rules and edge-injection safety)

Merge Readiness:

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

Verdict:

MERGE

Well-scoped PR that fully addresses the linked issue with clean data additions and valuable safety tests.

{
  "reviewed_sha": "bfaa05172539aae494802fc60a00170a604b0543",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 90,
  "recommendation": "MERGE"
}

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