Add treppe-gl shader renderer for treppe2000

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

shaders/flow.glsl

@@ -0,0 +1,10 @@
+// Rainbow flowing up the stairs
+vec3 hue(float h) {
+    return clamp(abs(mod(h * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0,
+                 0.0, 1.0);
+}
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord) {
+    float x = fragCoord.x / iResolution.x;
+    fragColor = vec4(hue(fract(x - iTime * 0.1)), 1.0);
+}

shaders/pulse.glsl

@@ -0,0 +1,7 @@
+// Warm white pulse travelling along the stairs
+void mainImage(out vec4 fragColor, in vec2 fragCoord) {
+    float x = fragCoord.x / iResolution.x;
+    float wave = 0.5 + 0.5 * sin(x * 6.2831 * 2.0 - iTime * 3.0);
+    vec3 warm = vec3(1.0, 0.45, 0.1);
+    fragColor = vec4(warm * wave, 1.0);
+}