Major update: synth styles, gradient sets, export dialogs, glass UI, docs

- Synth styles: blend any two renderers with five mix operations into
  brand-new generated looks, savable to localStorage as style chips
- Share codes bumped to v2 (synth fields), v1 codes still decode
- Gradient set generator: 4-12 seed variations with preview grid and
  ZIP batch download via a dependency-free store-only ZIP writer
- Export buttons now open dialogs with live preview and settings
- UI redesign: glassy translucent surfaces, rounder geometry, staggered
  intro animation, hover micro-interactions, refined scrollbars
- Docs page, generated favicon/touch icons and OG image, meta tags
- Skip chromatic aberration during synth blends to keep the D3D shader
  linker under its inlining limit

Co-authored-by: Cursor <cursoragent@cursor.com>

js/engine.js

@@ -17,7 +17,8 @@ var Engine = (function () {
     "u_scale", "u_complex", "u_warp", "u_flow", "u_stretch",
     "u_light", "u_gloss", "u_lightAngle", "u_irid", "u_glow",
     "u_grain", "u_cell", "u_lines", "u_ca", "u_vig", "u_soft",
-    "u_travel"
+    "u_travel",
+    "u_synth", "u_modeB", "u_mixOp", "u_blend"
   ];
 
   function compile(type, src) {
@@ -106,6 +107,11 @@ var Engine = (function () {
     gl.uniform1f(uniforms.u_soft, P.soft);
 
     gl.uniform1f(uniforms.u_travel, P.travel);
+
+    gl.uniform1i(uniforms.u_synth, P.synthOn ? 1 : 0);
+    gl.uniform1i(uniforms.u_modeB, P.modeB | 0);
+    gl.uniform1i(uniforms.u_mixOp, P.mixOp | 0);
+    gl.uniform1f(uniforms.u_blend, P.blend);
   }
 
   function renderAt(phase) {