refactor(worldgen): extract overworld lod helpers

[MichaelFisher1997]

Summary

• extract overworld LOD surface coloring into lod_coloring.zig
• extract overworld tree vegetation hint computation into tree_hints.zig
• keep material layering in overworld_generator.zig per issue scope

Verification

• nix develop --command zig fmt src/ modules/worldgen-overworld/src/lod_coloring.zig modules/worldgen-overworld/src/tree_hints.zig modules/worldgen-overworld/src/overworld_generator.zig modules/worldgen-overworld/src/root.zig
• nix develop --command zig build test

Closes #791

[github-actions]

📋 Summary

This PR closes #791, which requested extracting LOD surface coloring and tree vegetation hint logic from the 1,107-line overworld_generator.zig into dedicated collaborators (lod_coloring.zig and tree_hints.zig) while keeping material layering in place. The implementation matches the issue scope: the two modules are created, the generator is significantly slimmed down, behavior is preserved via a type-erased callback for classifyLODSample, and no RHI/threading code is touched. Verification (nix develop --command zig build test) passes and formatting is clean. Overall this is a focused, well-executed refactor.

📌 Review Metadata

• Reviewed Commit SHA: 32a9541aad025e509e970a00fd441490d0b420d3
• Reviewed PR: refactor(worldgen): extract overworld lod helpers #823
• Linked Issue: [SOLID] [M2] Extract LOD-coloring and tree-hints from overworld_generator.zig #791 — fully addressed.

🔴 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)

**[LOW]** `modules/worldgen-overworld/src/lod_coloring.zig:75` / `modules/worldgen-overworld/src/overworld_generator.zig:594`
**Confidence:** High
**Issue Title:** Duplicate `packFloatColor` helper
**Description:** The same `packFloatColor` function now exists in both `lod_coloring.zig` and `overworld_generator.zig` (the latter retained it for material-layer color packing).
**Impact:** Minor DRY violation; future color-format changes must be updated in two places.
**Suggested Fix:** Consider exporting `packFloatColor` from `lod_coloring.zig` and reusing it in `overworld_generator.zig`, or move it to a shared worldgen utility module if coupling material layers to LOD coloring is undesirable.

📊 SOLID Principles Score

Principle	Score	Notes
Single Responsibility	9	lod_coloring.zig and tree_hints.zig each own one clear concern.
Open/Closed	8	New modules are easy to extend; callback interface avoids direct coupling.
Liskov Substitution	10	No inheritance hierarchies involved.
Interface Segregation	8	ComputeParams/ClassifyFn are focused and minimal.
Dependency Inversion	7	tree_hints depends on an abstraction (callback) rather than concrete generator.
Average	8.4

🎯 Final Assessment

Overall Confidence Score: 90%

Confidence Breakdown:

• Code Quality: 90%
• Completeness: 95%
• Risk Level: 85%
• Test Coverage: 85%

Merge Readiness:

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

Verdict:

MERGE — Clean behavior-preserving refactor with passing tests and no safety concerns.

{
  "reviewed_sha": "32a9541aad025e509e970a00fd441490d0b420d3",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 90,
  "recommendation": "MERGE"
}

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