Highlight matching structures on UnitDisplay hover

Wires the existing ToggleStructureEvent (emitted on UnitDisplay button
mouseenter/leave) to view.setHighlightStructureTypes via a small
StructureHighlightController. StructurePass + StructureLevelPass already
implement the highlight visual — this just connects the two ends.

src/client/controllers/StructureHighlightController.ts

@@ -0,0 +1,28 @@
+/**
+ * StructureHighlightController — forwards UnitDisplay hover events to the
+ * renderer so matching structures glow while others dim.
+ *
+ * UnitDisplay emits ToggleStructureEvent on @mouseenter / @mouseleave for each
+ * unit-type button, with a payload of "production source" types
+ * (Warship → [Port], AtomBomb → [MissileSilo, SAMLauncher], building → itself).
+ * This controller just plumbs that payload to view.setHighlightStructureTypes;
+ * StructurePass + StructureLevelPass already implement the visual highlight.
+ */
+
+import { EventBus } from "../../core/EventBus";
+import { Controller } from "../Controller";
+import { ToggleStructureEvent } from "../InputHandler";
+import { GameView as WebGLGameView } from "../render/gl";
+
+export class StructureHighlightController implements Controller {
+  constructor(
+    private eventBus: EventBus,
+    private view: WebGLGameView,
+  ) {}
+
+  init() {
+    this.eventBus.on(ToggleStructureEvent, (e) =>
+      this.view.setHighlightStructureTypes(e.structureTypes),
+    );
+  }
+}