/claim #9681 Fix- #9681 Replace ConcurrentHashMap.newKeySet[A]() with Collections.newSetFromMap(new ConcurrentHashMap[A, java.lang.Boolean]()).

This approach:

• Avoids the buggy newKeySet method
• Maintains true concurrency (no synchronized fallback)
• Uses the standard Java pattern for concurrent sets
• Preserves JVM-equivalent performance