Function persist_to_blockfile_silent 

pub fn persist_to_blockfile_silent(
    block_id: &str,
    filename: &str,
    data: &[u8],
    filestore: Option<&Arc<FileStore>>,
    global_output_zone: Option<&str>,
)

and write-through to FileStore (if provided). Persist data to the block’s output file and the global transcript zone without publishing a WPS event. Used by the persistent controller to record user-message lines for future history loads (so that parseHistoryLines can reconstruct user_message nodes on reopen) without triggering a live-stream append that would produce a duplicate node alongside the agent-message-accepted UUID node. Same lazy-create semantics as handle_append_block_file.