📜 Description

Copy mutable collections (_contextDictionary, _tagDictionary, _extraDictionary, _fingerprintArray, _attributesDictionary) before passing them to scope observers in SentryScope.m. This prevents a race condition where observers dispatch async work that iterates the collection after the @synchronized lock is released, while another thread mutates it concurrently.

Also updates the misleading thread-safety comment in SentryWatchdogTerminationScopeObserver.swift to accurately describe the guarantee.

💡 Motivation and Context

Fixes a launch crash (EXC_BAD_ACCESS in objc_msgSend) reported in getsentry/sentry-react-native#5995 affecting <1% of cold launches on iOS 26+. The crash occurs because SentryWatchdogTerminationScopeObserver captures mutable collection references and dispatches async disk writes, racing with concurrent scope mutations.

The public getter methods (context, extras, tags, fingerprints, attributes) already return .copy — this fix makes observer notifications consistent with that pattern.

💚 How did you test it?

• Added testModifyingFromMultipleThreads_withObserverAsyncDispatch — a concurrent stress test that rapidly mutates scope context/tags/extras/fingerprint from multiple threads while an observer with async dispatch is active
• All existing SentryScopeSwiftTests (59 tests) pass
• All existing SentryWatchdogTerminationScopeObserverTests (18 tests) pass
• make format, make analyze, make build-ios all clean

📝 Checklist

You have to check all boxes before merging:

• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.