Add static_assert for deque age_t size

Author: John-194

include/dbscan/pbbs/scheduler.h

@@ -74,6 +74,9 @@ struct Deque {
     tag_t tag;
     qidx top;
   };
+  // Catches layout issues at compile time on platforms where age_t is not exactly 8 bytes,
+  // which would break the lock-free atomic CAS in the work-stealing deque.
+  static_assert(sizeof(age_t) == sizeof(int64_t), "age_t must be 8 bytes for atomic CAS");
 
   // align to avoid false sharing
   struct alignas(64) padded_job {