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, 44 insertions, 0 deletions

diff --git a/src/shaders/compute/gen_perlin.wgsl b/src/shaders/compute/gen_perlin.wgsl
new file mode 100644
index 0000000..2807f6d
--- /dev/null
+++ b/src/shaders/compute/gen_perlin.wgsl
@@ -0,0 +1,44 @@
+// GPU procedural Perlin noise texture generator.
+// Fractional Brownian Motion using value noise.
+
+#include "math/noise"
+
+struct PerlinParams {
+  width: u32,
+  height: u32,
+  seed: f32,
+  frequency: f32,
+  amplitude: f32,
+  amplitude_decay: f32,
+  octaves: u32,
+  _pad0: f32,  // Padding for alignment
+}
+
+@group(0) @binding(0) var output_tex: texture_storage_2d<rgba8unorm, write>;
+@group(0) @binding(1) var<uniform> params: PerlinParams;
+
+@compute @workgroup_size(8, 8, 1)
+fn main(@builtin(global_invocation_id) id: vec3<u32>) {
+  if (id.x >= params.width || id.y >= params.height) { return; }
+
+  let uv = vec2f(f32(id.x) / f32(params.width),
+                 f32(id.y) / f32(params.height));
+
+  var value = 0.0;
+  var amplitude = params.amplitude;
+  var frequency = params.frequency;
+  var total_amp = 0.0;
+
+  for (var o: u32 = 0u; o < params.octaves; o++) {
+    let p = uv * frequency + params.seed;
+    value += noise_2d(p) * amplitude;
+    total_amp += amplitude;
+    frequency *= 2.0;
+    amplitude *= params.amplitude_decay;
+  }
+
+  value /= total_amp;
+  let clamped = clamp(value, 0.0, 1.0);
+
+  textureStore(output_tex, id.xy, vec4f(clamped, clamped, clamped, 1.0));
+}