New effect family "Fluido": real-time GPU fluid simulation (ink-in-water)

Stable-fluids solver (fluid.js) on ping-pong half-float framebuffers:
semi-Lagrangian advection, vorticity confinement (clamped — unbounded
confinement overflows half-float and kills the field), 22 Jacobi pressure
iterations, audio-driven dye/force splats. Three wandering emitters inject
palette-coloured dye (brightness-normalized so dark palette entries stay
vivid); bass drives injection and stirring, beats fire directional bursts,
treble adds swirl. Universal modifiers map onto the sim: warp = vorticity,
speed = sim speed (brightness is speed-normalized), sym = kaleidoscope with
a wedge that rotates via rotSpeed, contrast/invert on display.

The Visualizer delegates to FluidSim when the preset has isFluid (flag is
always present so Object.assign merges can't leave it stale). 102 new
presets (17 palettes x 6 variants).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/output.html

@@ -42,6 +42,7 @@
 
   <script src="shaders.js"></script>
   <script src="effects.js"></script>
+  <script src="fluid.js"></script>
   <script src="visualizer.js"></script>
   <script src="audio.js"></script>
   <script src="output.js"></script>