Sam/factory radius ghost upgrade fix (#4104)

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**Add approved & assigned issue number here:**

Resolves #4059

## Description:

Makes ghost radius centred on building being upgrading (if upgrading
building)
<img width="1920" height="1080" alt="Screenshot from 2026-06-01
15-45-37"
src="https://github.com/user-attachments/assets/9cf19e59-0e20-4b43-b65f-35eebb37fa8e"
/>
<img width="1920" height="1080" alt="Screenshot from 2026-06-01
15-45-24"
src="https://github.com/user-attachments/assets/1953238f-5156-4bf7-aa18-8278c27d1a68"
/>


## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory

## Please put your Discord username so you can be contacted if a bug or
regression is found:

tktk123456

src/client/controllers/BuildPreviewController.ts

@@ -335,12 +335,24 @@ export class BuildPreviewController implements Controller {
         rangeRadius = this.game.config().defensePostRange();
         break;
     }
+    let radiusTileX = this.game.x(tileRef);
+    let radiusTileY = this.game.y(tileRef);
+    if (
+      rangeRadius > 0 &&
+      u.canUpgrade !== false &&
+      upgradeTargetTile !== null
+    ) {
+      radiusTileX = this.game.x(upgradeTargetTile);
+      radiusTileY = this.game.y(upgradeTargetTile);
+    }
 
     const cost = u.cost;
     return {
       ghostType: u.type,
       tileX: this.game.x(tileRef),
       tileY: this.game.y(tileRef),
+      radiusTileX,
+      radiusTileY,
       canBuild: u.canBuild !== false,
       canUpgrade: u.canUpgrade !== false,
       cost: Number(cost),

src/client/render/gl/passes/RangeCirclePass.ts

@@ -54,8 +54,8 @@ export class RangeCirclePass {
 
   updateGhostPreview(data: GhostPreviewData | null): void {
     if (data && data.rangeRadius > 0) {
-      this.centerX = data.tileX;
-      this.centerY = data.tileY;
+      this.centerX = data.radiusTileX;
+      this.centerY = data.radiusTileY;
       this.radius = data.rangeRadius;
       this.warning = data.rangeWarning;
     } else {

src/client/render/types/Renderer.ts

@@ -152,6 +152,8 @@ export interface GhostPreviewData {
   ghostType: string; // UnitType string ("City", "Port", etc.)
   tileX: number; // Hover tile X
   tileY: number; // Hover tile Y
+  radiusTileX: number;
+  radiusTileY: number;
   canBuild: boolean; // Valid placement?
   canUpgrade: boolean; // Upgrading existing structure?
   cost: number; // Gold cost