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, 53 insertions, 0 deletions

diff --git a/src/effects/particle_render.wgsl b/src/effects/particle_render.wgsl
new file mode 100644
index 0000000..ef0db42
--- /dev/null
+++ b/src/effects/particle_render.wgsl
@@ -0,0 +1,53 @@
+// Particle rendering (vertex + fragment) - V2
+struct Particle {
+    pos: vec4f,
+    vel: vec4f,
+    rot: vec4f,
+    color: vec4f,
+};
+
+#include "sequence_uniforms"
+
+@group(0) @binding(0) var<storage, read> particles: array<Particle>;
+@group(0) @binding(1) var<uniform> uniforms: UniformsSequenceParams;
+
+struct VSOut {
+    @builtin(position) pos: vec4f,
+    @location(0) color: vec4f,
+    @location(1) uv: vec2f,
+};
+
+@vertex fn vs_main(@builtin(vertex_index) vi: u32, @builtin(instance_index) ii: u32) -> VSOut {
+    let p = particles[ii];
+    let size = 0.02 + p.pos.z * 0.01 + uniforms.audio_intensity * 0.02;
+    var offsets = array<vec2f, 6>(
+        vec2f(-1, -1),
+        vec2f(1, -1),
+        vec2f(-1, 1),
+        vec2f(-1, 1),
+        vec2f(1, -1),
+        vec2f(1, 1)
+    );
+    let offset = offsets[vi];
+    let c = cos(p.rot.x);
+    let s = sin(p.rot.x);
+    let rotated_offset = vec2f(offset.x * c - offset.y * s, offset.x * s + offset.y * c);
+    let pos = vec2f(p.pos.x + rotated_offset.x * size / uniforms.aspect_ratio, p.pos.y + rotated_offset.y * size);
+
+    // Fade based on lifetime (p.pos.w goes from 1.0 to 0.0)
+    let lifetime_fade = p.pos.w;
+    let color_with_fade = vec4f(p.color.rgb * (0.5 + 0.5 * uniforms.audio_intensity), p.color.a * lifetime_fade);
+
+    return VSOut(vec4f(pos, 0.0, 1.0), color_with_fade, offset);
+}
+
+@fragment fn fs_main(@location(0) color: vec4f, @location(1) uv: vec2f) -> @location(0) vec4f {
+    // Calculate distance from center for circular shape
+    let dist = length(uv);
+
+    // Smooth circular falloff (1.0 at center, 0.0 at edge)
+    let circle_alpha = smoothstep(1.0, 0.5, dist);
+
+    // Apply circular fade to alpha channel
+    return vec4f(color.rgb, color.a * circle_alpha);
+}