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, 0 insertions, 27 deletions

diff --git a/common/shaders/compute/gen_mask.wgsl b/common/shaders/compute/gen_mask.wgsl
deleted file mode 100644
index 39f5b50..0000000
--- a/common/shaders/compute/gen_mask.wgsl
+++ /dev/null
@@ -1,27 +0,0 @@
-// This file is part of the 64k demo project.
-// GPU composite shader: Multiply texture A by texture B (masking).
-
-struct MaskParams {
-  width: u32,
-  height: u32,
-}
-
-@group(0) @binding(0) var output_tex: texture_storage_2d<rgba8unorm, write>;
-@group(0) @binding(1) var<uniform> params: MaskParams;
-@group(0) @binding(2) var input_a: texture_2d<f32>;
-@group(0) @binding(3) var input_b: texture_2d<f32>;
-@group(0) @binding(4) var tex_sampler: sampler;
-
-@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));
-
-  let color_a = textureSampleLevel(input_a, tex_sampler, uv, 0.0);
-  let mask_b = textureSampleLevel(input_b, tex_sampler, uv, 0.0);
-  let masked = color_a * mask_b;
-
-  textureStore(output_tex, id.xy, masked);
-}