[codex] Add selectable raster rendering path

[anirul]

Summary

Adds a rendering-mode override so examples can select auto, raytracing, or raster rendering from the command line while keeping the JSON scene files rendering agnostic.

Key changes:

• Adds --rendering={auto|raytrace|raytracing|rasterise|rasterising|rasterize|rasterizing|raster} handling in the common application/draw path.
• Builds raster level data from the existing raytracing-oriented JSON by removing raytrace resolve nodes, disabling acceleration structures, and wiring raster scene programs.
• Adds Vulkan and OpenGL raster GLTF shaders with PBR-style material inputs, environment lookup support, skinned mesh support, and shadow-map plumbing.
• Adds raster shadow-map rendering for Vulkan/OpenGL without reusing BVH/raytracing for shadows.
• Renames example 01_Raytracing to 01_Refraction and updates docs/examples.
• Fixes OpenGL window teardown order so GL-owned resources are destroyed while the context is current.

Validation

Ran locally from the main checkout:

• cmake --build --preset linux-debug --target FrameTest FrameJsonTest FrameVulkanTest FrameOpenGLTest
• ./build/linux-debug/tests/FrameTest --gtest_filter=DrawRenderingOverrideTest.*
• ./build/linux-debug/tests/FrameJsonTest --gtest_filter=ParseLevelTest.RasterOptionBuildsRasterSceneProgramForRaytracingJson:ParseLevelTest.RasterOptionKeepsSkinnedMeshAnimatedWithoutBvh:ParseLevelTest.RasterOptionKeepsCubemapOnlyLevelOnCubemapProgram:ParseLevelTest.RaytraceOptionKeepsCubemapOnlyLevelOnCubemapProgram
• ./build/linux-debug/tests/FrameVulkanTest --gtest_filter=VulkanSceneStateTest.*
• ./build/linux-debug/tests/FrameOpenGLTest --gtest_filter=WindowTest.DestroyWindowAfterLoadedRasterLevelKeepsContextAlive with display access
• ctest --test-dir build/linux-debug --output-on-failure -LE requires-opengl passed: 90/90 tests, with existing Vulkan hardware-dependent tests skipped
• git diff --check

Notes

The OpenGL teardown regression test is under FrameOpenGLTest; that target is labeled requires-opengl, so the hosted CI path that runs ctest -LE requires-opengl excludes it.