refactor(effects): co-locate effect WGSL shaders with their .h/.cc in src/effects/

Move 13 effect-specific shaders from workspaces/main/shaders/ to src/effects/
so each effect's .h, .cc, and .wgsl are together. Update assets.txt paths in
both main and test workspaces. Update EFFECT_WORKFLOW.md to reflect new location.
Shared/reusable snippets remain in src/shaders/.

handoff(Gemini): shaders moved; src/effects/ now has .h, .cc, and .wgsl per effect.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/effects/flash.wgsl b/src/effects/flash.wgsl
new file mode 100644
index 0000000..379086e
--- /dev/null
+++ b/src/effects/flash.wgsl
@@ -0,0 +1,27 @@
+// Flash shader for visual sync testing
+// Pulses white on beat
+#include "sequence_uniforms"
+
+@group(0) @binding(2) var<uniform> uniforms: UniformsSequenceParams;
+
+struct VertexOutput {
+    @builtin(position) position: vec4f,
+    @location(0) uv: vec2f,
+};
+
+@vertex fn vs_main(@builtin(vertex_index) vid: u32) -> VertexOutput {
+    var out: VertexOutput;
+    let x = f32((vid & 1u) << 1u);
+    let y = f32((vid & 2u));
+    out.position = vec4f(x * 2.0 - 1.0, 1.0 - y * 2.0, 0.0, 1.0);
+    out.uv = vec2f(x, y);
+    return out;
+}
+
+@fragment fn fs_main(in: VertexOutput) -> @location(0) vec4f {
+  // Strong flash on beat, fades quickly
+  let intensity = pow(1.0 - uniforms.beat_phase, 4.0);
+  // Add audio intensity for extra punch
+  let final_intensity = intensity * (1.0 + uniforms.audio_intensity * 0.5);
+  return vec4f(final_intensity, final_intensity, final_intensity, 1.0);
+}