Enhance InputHandler to allow using NumPad (#3317)

## Description:

Adds **Enter** and **Numpad Enter** as confirmation for placing a ghost
structure after selecting a building with hotkeys (1–0 or numpad).
Players can cancel with Esc but previously had to click to confirm; they
can now confirm with Enter or Numpad Enter at the current cursor
position. This supports keyboard-only or mouse + numpad workflows (e.g.
one hand on numpad for select + confirm, one on mouse for aiming).

## 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
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

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

.wozniakpl

src/client/graphics/layers/StructureIconsLayer.ts

@@ -17,6 +17,7 @@ import { TileRef } from "../../../core/game/GameMap";
 import { GameUpdateType } from "../../../core/game/GameUpdates";
 import { GameView, UnitView } from "../../../core/game/GameView";
 import {
+  ConfirmGhostStructureEvent,
   GhostStructureChangedEvent,
   MouseMoveEvent,
   MouseUpEvent,
@@ -43,6 +44,11 @@ import {
 } from "./StructureDrawingUtils";
 import bitmapFont from "/fonts/round_6x6_modified.xml?url";
 
+/** True for nuke types (AtomBomb, HydrogenBomb): ghost is preserved after placement so user can place multiple or keep selection (Enter/key confirm). */
+export function shouldPreserveGhostAfterBuild(unitType: UnitType): boolean {
+  return unitType === UnitType.AtomBomb || unitType === UnitType.HydrogenBomb;
+}
+
 extend([a11yPlugin]);
 
 class StructureRenderInfo {
@@ -92,6 +98,7 @@ export class StructureIconsLayer implements Layer {
   > = new Map(Structures.types.map((type) => [type, { visible: true }]));
   private lastGhostQueryAt: number;
   private visibilityStateDirty = true;
+  private pendingConfirm: MouseUpEvent | null = null;
   private hasHiddenStructure = false;
   potentialUpgrade: StructureRenderInfo | undefined;
 
@@ -171,7 +178,12 @@ export class StructureIconsLayer implements Layer {
     );
     this.eventBus.on(MouseMoveEvent, (e) => this.moveGhost(e));
 
-    this.eventBus.on(MouseUpEvent, (e) => this.createStructure(e));
+    this.eventBus.on(MouseUpEvent, (e) => this.requestConfirmStructure(e));
+    this.eventBus.on(ConfirmGhostStructureEvent, () =>
+      this.requestConfirmStructure(
+        new MouseUpEvent(this.mousePos.x, this.mousePos.y),
+      ),
+    );
 
     window.addEventListener("resize", () => this.resizeCanvas());
     await this.setupRenderer();
@@ -307,7 +319,10 @@ export class StructureIconsLayer implements Layer {
           this.ghostUnit.container.filters = [];
         }
 
-        if (!this.ghostUnit) return;
+        if (!this.ghostUnit) {
+          this.pendingConfirm = null;
+          return;
+        }
 
         const unit = buildables.find(
           (u) => u.type === this.ghostUnit!.buildableUnit.type,
@@ -322,6 +337,7 @@ export class StructureIconsLayer implements Layer {
           this.ghostUnit.container.filters = [
             new OutlineFilter({ thickness: 2, color: "rgba(255, 0, 0, 1)" }),
           ];
+          this.pendingConfirm = null;
           return;
         }
 
@@ -369,6 +385,14 @@ export class StructureIconsLayer implements Layer {
             : Math.min(1, scale / ICON_SCALE_FACTOR_ZOOMED_OUT);
         this.ghostUnit.container.scale.set(s);
         this.ghostUnit.range?.scale.set(this.transformHandler.scale);
+
+        if (this.pendingConfirm !== null) {
+          const ev = this.pendingConfirm;
+          this.pendingConfirm = null;
+          if (this.isGhostReadyForConfirm()) {
+            this.createStructure(ev);
+          }
+        }
       });
   }
 
@@ -399,6 +423,30 @@ export class StructureIconsLayer implements Layer {
       .fill({ color: 0x000000, alpha: 0.65 });
   }
 
+  /**
+   * True when the ghost exists and buildableUnit has been refreshed (canBuild or canUpgrade set).
+   * Used to avoid running createStructure before renderGhost's async buildables() has updated the ghost.
+   */
+  private isGhostReadyForConfirm(): boolean {
+    if (!this.ghostUnit) return false;
+    const bu = this.ghostUnit.buildableUnit;
+    return bu.canBuild !== false || bu.canUpgrade !== false;
+  }
+
+  /**
+   * Request confirm (place/upgrade): run createStructure now if ghost is ready, otherwise defer until
+   * renderGhost's buildables() callback has updated the ghost. Shared by Enter (ConfirmGhostStructureEvent)
+   * and mouse click (MouseUpEvent) so numpad-select-then-confirm works.
+   */
+  private requestConfirmStructure(e: MouseUpEvent): void {
+    if (!this.ghostUnit && !this.uiState.ghostStructure) return;
+    if (this.isGhostReadyForConfirm()) {
+      this.createStructure(e);
+    } else {
+      this.pendingConfirm = e;
+    }
+  }
+
   private createStructure(e: MouseUpEvent) {
     if (!this.ghostUnit) return;
     if (
@@ -420,6 +468,7 @@ export class StructureIconsLayer implements Layer {
           this.ghostUnit.buildableUnit.type,
         ),
       );
+      this.removeGhostStructure();
     } else if (this.ghostUnit.buildableUnit.canBuild) {
       const unitType = this.ghostUnit.buildableUnit.type;
       const rocketDirectionUp =
@@ -433,8 +482,12 @@ export class StructureIconsLayer implements Layer {
           rocketDirectionUp,
         ),
       );
+      if (!shouldPreserveGhostAfterBuild(unitType)) {
+        this.removeGhostStructure();
+      }
+    } else {
+      this.removeGhostStructure();
     }
-    this.removeGhostStructure();
   }
 
   private moveGhost(e: MouseMoveEvent) {
@@ -489,6 +542,7 @@ export class StructureIconsLayer implements Layer {
   }
 
   private clearGhostStructure() {
+    this.pendingConfirm = null;
     if (this.ghostUnit) {
       this.ghostUnit.container.destroy();
       this.ghostUnit.range?.destroy();