Fixes#14238. During a compression/session split at the response
boundary, the interim callback delivered unrelated commentary, setting
response_previewed=True. The suppression logic treated that as proof the
final reply had been delivered and skipped the normal send — the response
was persisted to the child session but never sent to chat.
Only suppress the normal final send when the stream consumer confirms
final delivery (final_response_sent / final_content_delivered) or the
exact final response text was delivered as a preview.
sgaofen
194bff0687