feat(tests): Add test_mesh tool for OBJ loading and normal visualization

Implemented a new standalone test tool 'test_mesh' to:
- Load a .obj file specified via command line.
- Display the mesh with rotation and basic lighting on a tiled floor.
- Provide a '--debug' option to visualize vertex normals as cyan lines.
- Updated asset_packer to auto-generate smooth normals for OBJs if missing.
- Fixed various WGPU API usage inconsistencies and build issues on macOS.
- Exposed Renderer3D::GetVisualDebug() for test access.
- Added custom Vec3 struct and math utilities for OBJ parsing.
This tool helps verify mesh ingestion and normal computation independently of the main demo logic.

1 files changed, 25 insertions, 2 deletions

diff --git a/src/3d/visual_debug.cc b/src/3d/visual_debug.cc
index 86f12b4..009a1e1 100644
--- a/src/3d/visual_debug.cc
+++ b/src/3d/visual_debug.cc
@@ -107,7 +107,7 @@ void VisualDebug::create_pipeline(WGPUTextureFormat format) {
 #if defined(DEMO_CROSS_COMPILE_WIN32)
   pipeline_desc.vertex.entryPoint = "vs_main";
 #else
-  pipeline_desc.vertex.entryPoint = {"vs_main", 7};
+  pipeline_desc.vertex.entryPoint = str_view("vs_main");
 #endif
   pipeline_desc.vertex.bufferCount = 1;
   pipeline_desc.vertex.buffers = &vertex_layout;
@@ -117,7 +117,7 @@ void VisualDebug::create_pipeline(WGPUTextureFormat format) {
 #if defined(DEMO_CROSS_COMPILE_WIN32)
   fragment_state.entryPoint = "fs_main";
 #else
-  fragment_state.entryPoint = {"fs_main", 7};
+  fragment_state.entryPoint = str_view("fs_main");
 #endif
   fragment_state.targetCount = 1;
 
@@ -203,6 +203,29 @@ void VisualDebug::add_aabb(const vec3& min, const vec3& max,
   }
 }
 
+void VisualDebug::add_mesh_normals(const mat4& transform, uint32_t num_vertices,
+                                   const MeshVertex* vertices) {
+  if (!vertices || num_vertices == 0)
+    return;
+
+  mat4 normal_matrix = mat4::transpose(transform.inverse());
+
+  for (uint32_t i = 0; i < num_vertices; ++i) {
+    const auto& v = vertices[i];
+
+    vec4 p_world = transform * vec4(v.p[0], v.p[1], v.p[2], 1.0f);
+    vec3 n_object = vec3(v.n[0], v.n[1], v.n[2]);
+    vec4 n_world_h = normal_matrix * vec4(n_object.x, n_object.y, n_object.z, 0.0f);
+    vec3 n_world = n_world_h.xyz().normalize();
+
+    lines_.push_back(
+        {p_world.xyz(), p_world.xyz() + n_world * 0.1f, // 0.1 is the length
+         {0.0f, 1.0f, 1.0f}                             // Cyan color
+        });
+  }
+}
+
+
 void VisualDebug::update_buffers(const mat4& view_proj) {
   // Update Uniforms
   wgpuQueueWriteBuffer(wgpuDeviceGetQueue(device_), uniform_buffer_, 0,