Remediation: Implement shared common/shaders/ directory

Eliminates 36 duplicate shader files across workspaces.

Structure:
- common/shaders/{math,render,compute}/ - Shared utilities (20 files)
- workspaces/*/shaders/ - Workspace-specific only

Changes:
- Created common/shaders/ with math, render, compute subdirectories
- Moved 20 common shaders from workspaces to common/
- Removed duplicates from test workspace
- Updated assets.txt: ../../common/shaders/ references
- Enhanced asset_packer.cc: filesystem path normalization for ../ resolution

Implementation: Option 1 from SHADER_REUSE_INVESTIGATION.md
- Single source of truth for common code
- Workspace references via relative paths
- Path normalization in asset packer

handoff(Claude): Common shader directory implemented

1 files changed, 44 insertions, 0 deletions

diff --git a/common/shaders/compute/gen_perlin.wgsl b/common/shaders/compute/gen_perlin.wgsl
new file mode 100644
index 0000000..73816d6
--- /dev/null
+++ b/common/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 = vec2<f32>(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, vec4<f32>(clamped, clamped, clamped, 1.0));
+}