restore alt-view (space hold) toggle

InputHandler still emits AlternateViewEvent on space down/up, and the
renderer still has setAltView. The bridge between them lived in
MapInteraction's applyAltView, which got deleted with the rest of
MapInteraction — nothing was wiring the event to the view anymore.
Expose view.setAltView and have ClientGameRunner subscribe.

src/client/render/gl/GameView.ts

@@ -321,6 +321,9 @@ export class GameView {
   setLocalPlayerID(id: number): void {
     this.renderer.setLocalPlayerID(id);
   }
+  setAltView(active: boolean): void {
+    this.renderer.setAltView(active);
+  }
   setHighlightOwner(ownerID: number): void {
     this.renderer.setHighlightOwner(ownerID);
   }