feat: add richer LOD source data

[MichaelFisher1997]

Summary

• Adds a version tag and optional fixed-budget vertical span storage to LOD source data.
• Keeps baseline surface-only LOD data valid for existing generators while allowing richer multi-layer columns when enabled.
• Adds tests for initialization, memory accounting, bounded span storage, and representative-column span seeding.

Verification

• nix develop --command zig fmt modules/world-core/src/lod_data.zig modules/world-core/src/root.zig
• nix develop --command zig build test

Fixes #688

[github-actions]

📋 Summary

This PR implements Issue #688 (Phase 2: introduce richer LOD source data). It adds a versioned LOD data structure with optional multi-layer vertical span support while maintaining backward compatibility with existing surface-only generators.

Linked Issue: #688 - Fully addressed. All acceptance criteria met:

• ✅ Multi-layer vertical representation via fixed-budget span storage (MAX_LOD_VERTICAL_SPANS = 4)
• ✅ Baseline surface-only path preserved via init() with optional fields disabled
• ✅ Bounded memory with totalMemoryBytes() accounting
• ✅ zig build test passes (verified, exit code 0)

📌 Review Metadata

• Reviewed Commit SHA: 710c88304afd65610098c51c2f1c661e4082ff9f
• Reviewed PR: feat: add richer LOD source data #694

The PR adds 184 lines across 2 files (modules/world-core/src/lod_data.zig and root.zig). It introduces LODDataVersion, LODVerticalSpan, optional vertical span arrays in LODSimplifiedData, and comprehensive unit tests. Code follows Zig conventions, uses proper errdefer cleanup, and maintains the existing API surface.

🔴 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	LODSimplifiedData manages LOD data; LODVerticalSpan is a clean data struct
Open/Closed	9	Extends existing struct without breaking existing generators
Liskov Substitution	10	No inheritance; optional fields preserve existing behavior
Interface Segregation	9	New types are exported individually; no fat interfaces
Dependency Inversion	8	Depends on world_core types appropriately
Average	9.0

🎯 Final Assessment

Overall Confidence Score: 95%

Confidence Breakdown:

• Code Quality: 95% (clean Zig idioms, proper memory safety, good test coverage)
• Completeness: 95% (fully addresses issue Phase 2: introduce richer LOD source data #688 requirements)
• Risk Level: 90% (low risk - additive change, optional fields, no breaking API changes)
• Test Coverage: 95% (tests for init, memory accounting, bounds, and representative seeding)

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 implementation that fully satisfies issue #688 with zero breaking changes.

{
  "reviewed_sha": "710c88304afd65610098c51c2f1c661e4082ff9f",
  "critical_issues": 0,
  "high_priority_issues": 0,
  "medium_priority_issues": 0,
  "overall_confidence_score": 95,
  "recommendation": "MERGE"
}

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