Remove the Snow visual preset

Snow is no longer offered anywhere a style can be chosen: the Visual
Presets tray, keyboard shortcut 7, the Cockpit vision carousel, and the
set_visual_style voice action. The shader and its labels go with it;
weather snowfall and the SNOW weather condition are unaffected.

Share links keep working. Snow's enum code (6) stays reserved, so a
compact or long-form link that names it opens on Normal and drops the
Snow shader parameters without reporting them as unknown. A Scene
Director shot saved with Snow plays on Normal too. Snow's frozen share
defaults matched Normal's apart from those parameters, so no other
setting in an old link changes meaning.

The legacy voice-schema pins restore Snow before hashing, so the
unchanged pins still prove nothing else moved; the complete Realtime
payload digest is re-derived.

src/styles/snow.js

@@ -1,97 +0,0 @@
-import { msg } from '../i18n/marker.js';
-
-/**
- * Snow Style — White overlay + Desaturation + Falling particles
- * Transforms the world into a winter wonderland
- */
-export const snowShader = {
-  name: 'snow',
-  uniforms: {
-    density: { default: 0.6, min: 0, max: 1, label: msg('Density') },
-    wind: { default: 0.5, min: 0, max: 1, label: msg('Wind') },
-  },
-  fragmentShader: /* glsl */ `
-    uniform sampler2D colorTexture;
-    uniform vec2 colorTextureDimensions;
-    uniform float intensity;
-    uniform float time;
-    uniform float density;
-    uniform float wind;
-    in vec2 v_textureCoordinates;
-
-    // Hash function for pseudo-random snow
-    float hash(vec2 p) {
-      p = fract(p * vec2(123.34, 456.21));
-      p += dot(p, p + 45.32);
-      return fract(p.x * p.y);
-    }
-
-    // Layered snow particles
-    float snowLayer(vec2 uv, float layer) {
-      float depth = 0.5 + layer * 0.5;
-      float speed = 0.4 + layer * 0.3;
-      float size = mix(0.01, 0.025, layer);
-      float windForce = 0.05 + wind * 0.2;
-
-      vec2 snowUV = uv * vec2(1.0, 0.5) * (4.0 + layer * 4.0);
-      snowUV.y += time * speed;
-      // Offset is the integral of a swaying velocity sin(time * 0.5 + phase) * windForce,
-      // so the sway stays bounded however long the app has been running.
-      snowUV.x -= 2.0 * cos(time * 0.5 + layer * 3.14) * windForce;
-
-      vec2 cell = floor(snowUV);
-      vec2 f = fract(snowUV);
-
-      float snow = 0.0;
-      // Check neighboring cells for smooth particles
-      for (int y = -1; y <= 1; y++) {
-        for (int x = -1; x <= 1; x++) {
-          vec2 neighbor = vec2(float(x), float(y));
-          vec2 point = vec2(hash(cell + neighbor), hash(cell + neighbor + 100.0));
-          // Animate particle position slightly
-          point = 0.5 + 0.4 * sin(time * 0.3 + 6.2831 * point);
-          float d = length(f - neighbor - point);
-          snow += smoothstep(size, 0.0, d) * depth;
-        }
-      }
-      return snow;
-    }
-
-    void main() {
-      vec2 uv = v_textureCoordinates;
-      vec4 color = texture(colorTexture, uv);
-
-      // Cool/blue color shift
-      vec3 cool = color.rgb * vec3(0.85, 0.9, 1.1);
-
-      // Desaturate partially
-      float luma = dot(cool, vec3(0.299, 0.587, 0.114));
-      vec3 desaturated = mix(cool, vec3(luma), 0.4 * intensity);
-
-      // Brighten (snow coverage lightens everything)
-      vec3 brightened = mix(desaturated, vec3(1.0), 0.15 * intensity);
-
-      // Add white frost overlay on brighter areas
-      float frostMask = smoothstep(0.3, 0.8, luma);
-      vec3 frosted = mix(brightened, vec3(0.95, 0.97, 1.0), frostMask * 0.25 * intensity);
-
-      // Accumulate snow particle layers (density controls amount)
-      float snow = 0.0;
-      snow += snowLayer(uv, 0.0) * 0.5;
-      snow += snowLayer(uv, 0.25) * 0.6;
-      snow += snowLayer(uv, 0.5) * 0.7;
-      snow += snowLayer(uv, 0.75) * 0.8;
-      snow += snowLayer(uv, 1.0) * 1.0;
-      snow = clamp(snow * (0.4 + density * 1.2), 0.0, 1.0);
-
-      // Composite snow particles
-      vec3 result = frosted + snow * 0.8 * intensity;
-
-      // Subtle fog in lower areas
-      float fog = smoothstep(0.0, 0.4, 1.0 - uv.y) * 0.1 * intensity;
-      result = mix(result, vec3(0.85, 0.88, 0.95), fog);
-
-      out_FragColor = vec4(mix(color.rgb, result, intensity), color.a);
-    }
-  `,
-};