drop the now-dead payloads from the sim-backed state-change events

TickAdvanced, BuildingBlocksChanged, ExpansionCostChanged, BossWaveUpdated and
ArtifactCountChanged all duplicated state the Simulation already owns. With
every subscriber re-reading from the sim, the fields had no readers left, so
the five events become payload-free refresh signals and the emitters keep the
values only as locals for change detection.

This makes the convention uniform: a state-change event backed by the
simulation carries nothing. Events whose state lives in the view (selection,
game speed, deconstruct and debug-draw modes) keep their payloads, since there
is no sim getter behind them.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/eventsystem/event/BossWaveUpdatedEvent.h

@@ -2,16 +2,11 @@
 #define BOSS_WAVE_UPDATED_EVENT_H
 
 #include "Event.h"
-#include "Tick.h"
 
+// Fired when the boss wave counter or its countdown changes. Carries no payload —
+// subscribers re-read Simulation::getBossWaveCounter() and getBossCountdownTicks().
 class BossWaveUpdatedEvent : public Event
 {
-public:
-	BossWaveUpdatedEvent(int counter, Tick countdownTicks)
-	    : counter(counter), countdownTicks(countdownTicks) {}
-	const int  counter;
-	const Tick countdownTicks;
 };
 
 #endif   // BOSS_WAVE_UPDATED_EVENT_H
-