move pan input into an InputMapper

src/lib/eventsystem/event/PanDirectionChangedEvent.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "Event.h"
+#include "WorldCamera.h"
+
+// The direction the player is currently panning the view has changed
+// (REQ-UI-SCROLL). Deliberately level-triggered: the payload is the complete
+// current direction, including PanDirection::None when panning stops, rather than
+// separate started/stopped events. A receiver that only ever saw edges would have
+// to reconstruct the state and would be left panning forever if one edge went
+// missing — which is exactly what happens when the widget loses focus mid-pan.
+//
+// Unlike the state-change events elsewhere in the UI, the receiver does cache this
+// payload instead of re-reading the value from somewhere authoritative. That is
+// correct here: input has no other source of truth to re-read from, so the
+// publisher (InputMapper) is the authority and the payload is the value.
+class PanDirectionChangedEvent : public Event
+{
+public:
+    explicit PanDirectionChangedEvent(PanDirection direction) : direction(direction) {}
+    const PanDirection direction;
+};