An exception thrown inside a `when` filter is swallowed as false, so a manifest
re-read failing mid-File.Replace turned a race that should retry into a thrown
torn-page error. The re-read now runs in the handler, and a failed re-read
counts as moved. Parallel.For's AggregateException is unwrapped where the pages
are read, so the page's own failure propagates and the torn check no longer
walks wrappers.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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