Fix clouds3d: move starField out of main() (GLSL syntax)

GLSL does not allow nested function definitions; the starField()
helper must live at top-level alongside hash3/noise3/fbm3.

vendor/clouds3d.js

@@ -98,6 +98,20 @@ var FRAG_SRC = [
         'profile = max(profile, 0.0);',
         'return smoothstep(baseThresh, baseThresh + 0.18, n) * profile;',
     '}',
+    // Star field: project ray onto a far sphere, hash-grid for
+    // positions. Visible above the horizon at night with a small
+    // twinkle.
+    'float starField(vec3 r) {',
+        'vec3 sp = r * 220.0;',
+        'vec3 sf = floor(sp);',
+        'vec3 sfp = fract(sp) - 0.5;',
+        'float h = hash3(sf);',
+        'float starD = length(sfp);',
+        'float mask = step(0.985, h) * smoothstep(0.35, 0.0, starD);',
+        'float twinkle = 0.55 + 0.45 * sin(uTime * 3.0 + h * 47.0);',
+        'return mask * twinkle;',
+    '}',
+    '}',
     'void main() {',
         'vec2 uv = (gl_FragCoord.xy / uResolution.xy) * 2.0 - 1.0;',
         'uv.x *= uResolution.x / uResolution.y;',
@@ -115,20 +129,7 @@ var FRAG_SRC = [
         // Sky gradient based on ray Y (background).
         'float skyT = clamp(rd.y * 0.7 + 0.5, 0.0, 1.0);',
         'vec3 col = mix(uBg, uSky, skyT);',
-        // Stars: project ray onto a far sphere, hash-grid for star
+        // Stars: hash-grid sphere, above horizon, only at night.
-        // positions. Only visible above the horizon and at night,
-        // with a small twinkle so they don't look like a static
-        // dither pattern.
-        'float starField(vec3 r) {',
-            'vec3 sp = r * 220.0;',
-            'vec3 sf = floor(sp);',
-            'vec3 sfp = fract(sp) - 0.5;',
-            'float h = hash3(sf);',
-            'float starD = length(sfp);',
-            'float mask = step(0.985, h) * smoothstep(0.35, 0.0, starD);',
-            'float twinkle = 0.55 + 0.45 * sin(uTime * 3.0 + h * 47.0);',
-            'return mask * twinkle;',
-        '}',
         'float stars = starField(rd) * smoothstep(0.05, 0.35, rd.y) * (1.0 - uDayProgress);',
         'col = mix(col, uLight, clamp(stars, 0.0, 1.0) * 0.9);',
         // Density threshold: weather 'sunny' -> high (sparse clouds),