Function publish_transcript_changed 

pub fn publish_transcript_changed(
    broker: &Broker,
    block_id: &str,
    fileop: &str,
    filestore: &FileStore,
)

Tell a block’s panes that its transcript output was replaced or deleted as a whole (Phase 5a-3), so an open pane resyncs at once instead of on its next read. fileop is mps::FILE_OP_REPLACE — with the new generation and line count read from filestore — or mps::FILE_OP_DELETE. Call it, with the replace or delete itself, inside with_transcript_order.