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, 32 insertions, 0 deletions

diff --git a/src/shaders/gaussian_blur.wgsl b/src/shaders/gaussian_blur.wgsl
new file mode 100644
index 0000000..7f85719
--- /dev/null
+++ b/src/shaders/gaussian_blur.wgsl
@@ -0,0 +1,32 @@
+// Gaussian blur shader for Sequence v2
+#include "sequence_uniforms"
+#include "render/fullscreen_uv_vs"  // <- VertexOutput + vs_main
+
+@group(0) @binding(0) var input_sampler: sampler;
+@group(0) @binding(1) var input_texture: texture_2d<f32>;
+@group(0) @binding(2) var<uniform> uniforms: UniformsSequenceParams;
+
+struct GaussianBlurParams {
+    direction: vec2f,
+    radius: f32,
+    _pad: f32,
+};
+@group(0) @binding(3) var<uniform> params: GaussianBlurParams;
+
+@fragment fn fs_main(in: VertexOutput) -> @location(0) vec4f {
+    let texel_size = 1.0 / uniforms.resolution;
+    let offset = params.direction * texel_size;
+
+    var color = vec4f(0.0);
+    let kernel_size = i32(params.radius);
+    var weight_sum = 0.0;
+
+    for (var i = -kernel_size; i <= kernel_size; i++) {
+        let sample_offset = f32(i) * offset;
+        let weight = exp(-f32(i * i) / (2.0 * params.radius * params.radius));
+        color += textureSample(input_texture, input_sampler, in.uv + sample_offset) * weight;
+        weight_sum += weight;
+    }
+
+    return color / weight_sum;
+}