move the remaining hotkeys into the InputMapper

src/lib/eventsystem/event/ModeCancelRequestedEvent.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "Event.h"
+
+// The player pressed the one "get me out of the current mode" key (REQ-UI-HOTKEYS).
+// Intentionally says only that, not which mode to leave: which of builder,
+// blueprint placement, or deconstruct is active — and that the key falls through to
+// entering deconstruct mode when none of them is — is state only the receiver has.
+class ModeCancelRequestedEvent : public Event
+{
+public:
+    ModeCancelRequestedEvent() = default;
+};