fix(3d): VisualDebug uniform buffer size mismatch

Fixed validation error in test_3d_render:
- Uniform buffer was 64 bytes (mat4) but bind group expected 176 bytes (GlobalUniforms)
- Updated buffer creation to use sizeof(GlobalUniforms)
- Updated bind group entry size to match
- Updated update_buffers to write full GlobalUniforms struct

Error was:
  Binding size 64 of Buffer with '' label is less than minimum 176

Root cause: VisualDebug uses same GlobalUniforms structure as main renderer
but was only allocating/binding mat4 portion.

Testing:
- All 34 tests passing (100%)
- test_3d_render runs without validation errors
- GPU procedural textures working (noise, perlin, grid)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/src/3d/visual_debug.cc b/src/3d/visual_debug.cc
index 77311f6..cd4ccce 100644
--- a/src/3d/visual_debug.cc
+++ b/src/3d/visual_debug.cc
@@ -26,7 +26,7 @@ void VisualDebug::init(WGPUDevice device, WGPUTextureFormat format) {
 
   WGPUBufferDescriptor ub_desc = {};
   ub_desc.usage = WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst;
-  ub_desc.size = sizeof(mat4);
+  ub_desc.size = sizeof(GlobalUniforms);
   uniform_buffer_ = wgpuDeviceCreateBuffer(device_, &ub_desc);
 }
 
@@ -340,9 +340,12 @@ void VisualDebug::add_trajectory(const std::vector<vec3>& points,
 }
 
 void VisualDebug::update_buffers(const mat4& view_proj) {
-  // Update Uniforms
+  // Update Uniforms - fill entire GlobalUniforms structure
+  GlobalUniforms uniforms = {};
+  uniforms.view_proj = view_proj;
+  // Other fields zeroed (not used by visual debug shader)
   wgpuQueueWriteBuffer(wgpuDeviceGetQueue(device_), uniform_buffer_, 0,
-                       &view_proj, sizeof(mat4));
+                       &uniforms, sizeof(GlobalUniforms));
 
   // Update Vertices
   size_t required_size = lines_.size() * 2 * sizeof(float) * 6;
@@ -385,7 +388,7 @@ void VisualDebug::update_buffers(const mat4& view_proj) {
     WGPUBindGroupEntry bg_entry = {};
     bg_entry.binding = 0;
     bg_entry.buffer = uniform_buffer_;
-    bg_entry.size = sizeof(mat4);
+    bg_entry.size = sizeof(GlobalUniforms);
 
     WGPUBindGroupDescriptor bg_desc = {};
     bg_desc.layout = bind_group_layout_;