B3: NIF V3.1 parser #141

Summary

Implement a minimal NIF V3.1 binary parser that can load Bridge Commander ship models. Target: ~2-3K LOC.

Scope

Parse the NIF classes needed for ship rendering:

• NiNode (scene hierarchy)
• NiTriShape / NiTriShapeData (mesh geometry: vertices, normals, UVs, indices)
• NiTexturingProperty + NiSourceTexture (texture references)
• NiMaterialProperty (material colors)
• NiAlphaProperty (alpha blending)
• NiZBufferProperty (depth buffer settings)
• NiVertexColorProperty
• NiKeyframeController + NiKeyframeData (animation, deferred to B8)

Reference Resources

• `engine/nif.xml` -- NIF format spec with V3.1 field definitions
• `engine/gamebyro-1.2-source/` -- Gamebryo 1.2 source for algorithms
• `engine/mwse/` -- MWSE headers for struct offsets
• NifSkope for visual validation

Acceptance Criteria

• Loads a BC ship .nif file without crashing
• Extracts vertex/index/normal/UV data for all mesh nodes
• Extracts texture file references
• Builds a scene hierarchy matching the NIF node tree
• Validated against NifSkope visualization for at least 3 stock ships
• Unit tests for NIF header parsing, node traversal

Blocks: #120