Apple Inc.’s long-planned upgrade to the Siri virtual assistant has run into snags during testing in recent weeks, potentially pushing back the release of several highly anticipated functions.After planning to include the new capabilities in iOS 26.4 — an operating system update slated for March — Apple is now working to spread them out over future versions, according to people familiar with the matter. That would mean possibly postponing at least some features until at least iOS 26.5, due in Ma...