0.17.1

Fixed

• Sync links document URLs introduced by edits to previously stored messages, including text edits
  saved by older messaging SDKs. Unchanged documents do not need another download; repeated sync
  keeps one link per message. The messenger must have saved the edit locally first.
• The first sync with the new linker repairs earlier missed message links, even if an older sync
  already advanced its checkpoint. The local pass is retried on failure and does not redownload
  unchanged document content.