refactor: move common/shaders/ to src/shaders/

Relocates shared WGSL shaders under src/ where all source code lives,
eliminating the top-level common/ directory.

- Update asset references in workspaces/main/assets.txt and workspaces/test/assets.txt
- Update docs: PROJECT_CONTEXT.md, ARCHITECTURE.md, WORKSPACE_SYSTEM.md, SHADER_REUSE_INVESTIGATION.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/shaders/skybox.wgsl b/src/shaders/skybox.wgsl
new file mode 100644
index 0000000..075eeb6
--- /dev/null
+++ b/src/shaders/skybox.wgsl
@@ -0,0 +1,24 @@
+#include "common_uniforms"
+#include "math/common_utils"
+#include "render/fullscreen_uv_vs"  // <- VertexOutput + vs_main
+
+@group(0) @binding(0) var sky_tex: texture_2d<f32>;
+@group(0) @binding(1) var sky_sampler: sampler;
+@group(0) @binding(2) var<uniform> globals: GlobalUniforms;
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4f {
+    // Convert UV to NDC
+    let ndc_x = in.uv.x * 2.0 - 1.0;
+    let ndc_y = (1.0 - in.uv.y) * 2.0 - 1.0; // Un-flip Y for NDC (Y-up)
+    
+    // Unproject to find world direction
+    // We want the direction from camera to the far plane at this pixel
+    let clip_pos = vec4f(ndc_x, ndc_y, 1.0, 1.0);
+    let world_pos_h = globals.inv_view_proj * clip_pos;
+    let world_pos = world_pos_h.xyz / world_pos_h.w;
+    
+    let ray_dir = normalize(world_pos - globals.camera_pos_time.xyz);
+    let uv = spherical_uv_from_dir(ray_dir);
+    return textureSample(sky_tex, sky_sampler, uv);
+}
\ No newline at end of file