feat: implement Phase 1 foundation - triangle rendering
- voltex_math: Vec3 with arithmetic ops, dot, cross, length, normalize
- voltex_platform: VoltexWindow (winit wrapper), InputState (keyboard/mouse),
GameTimer (fixed timestep + variable render loop)
- voltex_renderer: GpuContext (wgpu init), Vertex + buffer layout,
WGSL shader, render pipeline
- triangle example: colored triangle with ESC to exit
All 13 tests passing. Window renders RGB triangle on dark background.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
tolelom
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