We got a skybox

destrum/assets_src/shaders/skybox.frag

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+#version 450
+#extension GL_GOOGLE_include_directive : require
+#extension GL_EXT_nonuniform_qualifier : enable
+
+#include "bindless.glsl"
+
+layout(location = 0) in vec2 uv;      // from fullscreen triangle: 0..2 range
+layout(location = 0) out vec4 outColor;
+
+layout(push_constant) uniform SkyboxPC {
+    mat4 invViewProj;        // inverse(Proj * View) (your current setup)
+    vec4 cameraPos;          // xyz = camera world position
+    uint skyboxTextureId;    // index into textureCubes[]
+} pcs;
+
+void main()
+{
+    // Fullscreen-triangle trick gives uv in [0..2]. Convert to [0..1].
+    vec2 uv01 = uv * 0.5;
+
+    // Build an NDC point on the far plane.
+    // Vulkan NDC is x,y in [-1..1], z in [0..1]. Using z=1 means "far".
+    vec4 ndc = vec4(uv01 * 2.0 - 1.0, 1.0, 1.0);
+
+    // Unproject to world space
+    vec4 world = pcs.invViewProj * ndc;
+    vec3 worldPos = world.xyz / world.w;
+
+    // Direction from camera through this pixel
+    vec3 dir = normalize(worldPos - pcs.cameraPos.xyz);
+
+    // Sample cubemap directly
+    outColor = sampleTextureCubeLinear(pcs.skyboxTextureId, dir);
+    // outColor = sampleTextureCubeNearest(pcs.skyboxTextureId, dir);
+}