feat: draw all raster particle states

shaders/particle_gpu_validation.fragment.glsl

@@ -40,8 +40,15 @@ void main() {
         if (any(isnan(velocity))) position = v_uv;
         fragColor = vec4(position, fract(previous.b + 0.03125 * u_pass.y), 1.0);
     } else if (mode < 1.5) {
-        // The trail consumes State B/A written by the real field-sampling pass.
-        // Four deterministic texels are enough for the Stage A visual proof.
+        // Formal Trail first fades the previous target. Its full-particle point
+        // draw follows in the same target and consumes every State texel.
+        if (u_mask.z > 0.5) {
+            fragColor = vec4(previous.rgb * u_marker.w, 1.0);
+            return;
+        }
+
+        // LEGACY VALIDATION DISPLAY: retain the original four deterministic
+        // samples for the historical ParticleValidationLayer only.
         float marker = 0.0;
         marker = max(marker, 1.0 - smoothstep(0.0, u_marker.z, distance(v_uv, texture(u_state_texture, vec2(0.125, 0.125)).rg)));
         marker = max(marker, 1.0 - smoothstep(0.0, u_marker.z, distance(v_uv, texture(u_state_texture, vec2(0.375, 0.375)).rg)));
@@ -49,6 +56,11 @@ void main() {
         marker = max(marker, 1.0 - smoothstep(0.0, u_marker.z, distance(v_uv, texture(u_state_texture, vec2(0.875, 0.875)).rg)));
         vec3 color = previous.rgb * u_marker.w + marker * vec3(0.08, 0.55, 1.0);
         fragColor = vec4(min(color, vec3(1.0)), 1.0);
+    } else if (mode > 3.5) {
+        // The vertex shader fetched this particle's State texel directly from
+        // the current State write texture. Every point contributes one formal
+        // particle draw; no CPU position data is involved per frame.
+        fragColor = vec4(0.08, 0.55, 1.0, 1.0);
     } else {
         // The formal RasterParticle layer displays the Trail texture written by
         // the current State -> Trail pass. Legacy ParticleValidation keeps its

shaders/particle_gpu_validation.vertex.glsl

@@ -10,11 +10,22 @@ layout (std140) uniform ParticleGpuValidationUBO {
     highp mat4 u_matrix;
 };
 
+uniform sampler2D u_state_texture;
+
 void main() {
     v_uv = a_pos;
     v_world = a_pos;
     if (u_pass.x < 1.5) {
         gl_Position = vec4(a_pos * 2.0 - 1.0, 0.0, 1.0);
+    } else if (u_pass.x > 3.5) {
+        // 40-03: a_pos is a static State texel index generated only when the
+        // particle capacity changes. The position itself remains GPU-owned.
+        vec2 stateUV = (a_pos + vec2(0.5)) / u_mask.xy;
+        vec2 position = texture(u_state_texture, stateUV).rg;
+        v_uv = position;
+        v_world = position;
+        gl_PointSize = 3.0;
+        gl_Position = vec4(position * 2.0 - 1.0, 0.0, 1.0);
     } else {
         // VALIDATION ONLY: a_pos is canonical z0 world geometry; u_matrix is
         // PaintParameters::matrixForTile() for the selected MapLibre world copy.