[beekld]

Summary

Since #489, the data system has silently ignored a synchronizer result with State: Off. The result's error was dropped, the status didn't change, and the data system kept waiting on that synchronizer. A synchronizer isn't supposed to report Off, but State is a public field, and custom synchronizers can set it.

This PR treats an Off result as an unexpected failure. The data system reports Interrupted with the result's error and parks the synchronizer.

It also changes how the data system handles a synchronizer that closes its result channel on its own. That used to count as a fallback, which with a single synchronizer restarted it at once with no delay. A synchronizer that kept ending its results could then restart in a tight loop. The data system now treats this as an unexpected failure too, and parks the synchronizer.

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Note

Overview
Fixes FDv2 synchronizer handling where State: Off from a synchronizer was ignored (error dropped, loop kept waiting) and where a synchronizer closing its own result channel was treated like a normal fallback—often restarting immediately with a single synchronizer and risking a tight loop.

Off results are now treated as an unexpected failure: status becomes Interrupted with the result’s error, and the synchronizer is parked (same path as other unexpected failures).

A closed result channel is also an unexpected failure: status Interrupted with a fixed unknown error message, then syncPark (or syncRestart if the SDK key changed mid-run). Tests cover both behaviors.

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