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, 11 insertions, 0 deletions

diff --git a/src/shaders/passthrough.wgsl b/src/shaders/passthrough.wgsl
new file mode 100644
index 0000000..bce377c
--- /dev/null
+++ b/src/shaders/passthrough.wgsl
@@ -0,0 +1,11 @@
+// Passthrough 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;
+
+@fragment fn fs_main(in: VertexOutput) -> @location(0) vec4f {
+    return textureSample(input_texture, input_sampler, in.uv);
+}