fix: correct matrix order (proj*view) + Z depth range for Vulkan

- VP matrix order: proj*view (GLSL column-vector convention)
- Z correction in vertex shader: gl_Position.z = (z+w)*0.5 (OpenGL [-1,1] → Vulkan [0,1])
- Depth test temporarily disabled for debugging

src/Engine.Graphics.Vulkan/Shaders/triangle.vert

@@ -17,6 +17,7 @@ layout(row_major, push_constant) uniform PC {
 
 void main() {
     gl_Position = vp * pc.model * vec4(inPosition, 1.0);
+    gl_Position.z = (gl_Position.z + gl_Position.w) * 0.5;
     fragColor = inColor;
     fragNormal = mat3(pc.model) * inNormal;
 }