feat(render3d): a bole that does not quake, leaves out of the lens, a light with a reach

layer_flutter's mask was the vertex's height alone, so on a ten metre aspen every part of
the trunk above 1.2 m trembled with the leaves and the bole read as cloth. What separates
a leaf from a bole is distance from the model's centre line, not height; the mask is
radial now, and small plants keep the old one because a flower is all leaf.

NEAR_FADE dithers tree foliage out inside arm's length of the camera, in the depth
prepass, so the lit pass never sees those pixels and the equal-depth optimisation is
untouched. gl_Position.w is the view depth, so it costs one varying and no uniform.
Blades, cards and flowers are excluded - they live at the player's feet - and the shadow
pass keeps every leaf.

daylight_hand takes a reach in metres. The falloff was an inverse square windowed between
26 and 6 with both numbers hard-coded: two per cent of its own near field at ten metres,
so a torch lit your boots. It is a gentle power out to the reach now.

Measured in Maroon Lake, twice per side: the crown mask moves 1.7% of an aspen frame and
nothing at all in the meadow under it; the near fade moves 7.1% of a first-person frame
at a conifer and 0% where there is no foliage in the lens; the torch's reach lifts the lit
ground 20 to 45% and leaves the sky bit-identical.

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

packages/ludic.render3d/shaders/model.frag

@@ -5,6 +5,7 @@ in float v_seed;
 in vec2 v_rot;
 in float v_hull;
 in float v_quake;   // an aspen leaf turning its pale side up
+in float v_near;    // 0 in the camera's face, 1 past arm's length (NEAR_FADE)
 uniform float u_model_h;
 out vec4 o_color;
 uniform sampler2D u_diff;
@@ -38,6 +39,10 @@ void main() {
   //  early depth rejection off and bring the overdraw back, and the prepass has already
   //  cut both the clip plane and the alpha)
   if (v_wpos.y < u_clip_y) discard;
+#ifdef NEAR_FADE
+  // the same dither as the prepass, for the draws that have no prepass in front of them
+  if (v_near < 0.999 && v_near < fract(sin(dot(gl_FragCoord.xy, vec2(12.9898, 78.233))) * 43758.5453)) discard;
+#endif
 #endif
   vec3 N = normalize(v_nrm);
   if (!gl_FrontFacing && v_hull >= 0.0) N = -N;