feat(traps): activation VFX/SFX, explosion effect, and help section

Wire mimic/pit/arrow/laser media on activate, poison/explosion via effects, and document the scene editor and traps in Instructions.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/editor/EditorApp.tsx

@@ -274,7 +274,7 @@ export function EditorApp() {
 
   useEffect(() => {
     setSelectedGraphNodeId(null);
-  }, [state.project?.id]);
+  }, [state.project?.id, state.openingProjectId]);
 
   useEffect(() => {
     if (!state.project || !selectedGraphNodeId) return;