feat(3d): Implement scene query shadows (POC)

- Updated Renderer3D shader to include 'map_scene' and 'calc_shadow' functions.
- Shader now iterates over all objects (up to kMaxObjects) to evaluate the scene SDF globally.
- Implemented hard/soft shadows from a fixed directional light.
- Updated GlobalUniforms struct with proper packing/padding for WebGPU compatibility.
- Captured 'GPU BVH & Shadows' task in PROJECT_CONTEXT.md for future optimization.

1 files changed, 1 insertions, 0 deletions

diff --git a/TODO.md b/TODO.md
index b4c2f58..19097da 100644
--- a/TODO.md
+++ b/TODO.md
@@ -22,6 +22,7 @@ This file tracks the next set of immediate, actionable tasks for the project.
            == Can this std::vector<T> be replaced by a simple C-like "const T*" array?
            == are these std::string needed or can they be replaced by some 'const char*' ?
            == etc.
+    - [ ] the inclusion of gpu.h (either "gpu.h" or <webgpu/gpu.h>) seems to be a recurring compilation and portability issue. Can we have a single inclusion of gpu.h in some platform header instead of scattered inclusion in .cc files? This would reduce the single-point-of-compilation failures during compilation and portability checks.
 
 ## Future Goals