- insertMessages uses INSERT OR IGNORE on (mailboxId, uid) conflict instead of crashing on UNIQUE constraint when messages are re-fetched after restart - IMAPResponseHandler.sendCommand resumes any leaked previous continuation before registering a new one, preventing DuplicateCommandTag errors - add channelInactive handler to resume pending continuations on connection drop - add error type to sync failure log for better diagnostics Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>