add configurable dot size for zoomed-out structures

Structures collapse to a dot when zoomed out past dotsZoomThreshold.
The dot scale was hardcoded to 1.0 / 2.5 (≈0.4) in structure.vert.glsl.

Promote it to a render setting (`structure.dotScale`) so it's tunable
alongside iconSize / dotsZoomThreshold. Default 0.4 preserves current
behavior. Plumbed via uDotScale uniform on StructurePass.

src/client/render/gl/passes/structure-pass.ts

@@ -74,6 +74,7 @@ export class StructurePass {
   private uZoom: WebGLUniformLocation;
   private uIconSize: WebGLUniformLocation;
   private uDotsThreshold: WebGLUniformLocation;
+  private uDotScale: WebGLUniformLocation;
   private uScaleFactor: WebGLUniformLocation;
   private uShapeScales: WebGLUniformLocation;
   private uIconFills: WebGLUniformLocation;
@@ -140,6 +141,7 @@ export class StructurePass {
     this.uCamera = gl.getUniformLocation(this.program, "uCamera")!;
     this.uZoom = gl.getUniformLocation(this.program, "uZoom")!;
     this.uIconSize = gl.getUniformLocation(this.program, "uIconSize")!;
+    this.uDotScale = gl.getUniformLocation(this.program, "uDotScale")!;
     this.uDotsThreshold = gl.getUniformLocation(
       this.program,
       "uDotsThreshold",
@@ -330,6 +332,7 @@ export class StructurePass {
     gl.uniform1f(this.uZoom, zoom);
     gl.uniform1f(this.uIconSize, ss.iconSize);
     gl.uniform1f(this.uDotsThreshold, ss.dotsZoomThreshold);
+    gl.uniform1f(this.uDotScale, ss.dotScale);
     gl.uniform1f(this.uScaleFactor, ss.iconScaleFactorZoomedOut);
 
     // Build per-structure uniform arrays from settings, ordered by atlas column

src/client/render/gl/render-settings.json

@@ -82,9 +82,10 @@
     "railAlpha": 1
   },
   "structure": {
-    "iconSize": 35,
+    "iconSize": 65,
-    "dotsZoomThreshold": 0.5,
+    "dotsZoomThreshold": 1.2,
-    "iconScaleFactorZoomedOut": 1.4,
+    "dotScale": 0.3,
+    "iconScaleFactorZoomedOut": 3.5,
     "shapes": {
       "City": {
         "scale": 1,

src/client/render/gl/render-settings.ts

@@ -86,6 +86,8 @@ export interface RenderSettings {
   structure: {
     iconSize: number;
     dotsZoomThreshold: number;
+    /** Icon size multiplier when zoomed out past dotsZoomThreshold. */
+    dotScale: number;
     iconScaleFactorZoomedOut: number;
     shapes: Record<string, { scale: number; iconFill: number }>;
     highlightOutlineWidth: number;

src/client/render/gl/shaders/structure/structure.vert.glsl

@@ -12,6 +12,7 @@ uniform float uZoom;
 
 uniform float uIconSize;
 uniform float uDotsThreshold;
+uniform float uDotScale;
 uniform float uScaleFactor;
 uniform float uShapeScales[ATLAS_COLS];
 uniform float uIconFills[ATLAS_COLS];
@@ -36,7 +37,7 @@ void main() {
 
   float iconScale;
   if (uZoom <= uDotsThreshold) {
-    iconScale = 1.0 / 2.5;
+    iconScale = uDotScale;
   } else {
     iconScale = min(1.0, uZoom / uScaleFactor);
   }