Function report_error 

pub unsafe fn report_error(
    out_err: *mut FolditPluginError,
    e: &PluginError,
) -> FolditPluginStatus

Populate out_err and pick the status the host should see. Unsupported maps to the dedicated status so the host can distinguish “plugin has no streaming” from “streaming failed”.

Safety

out_err must be null or point to a writable FolditPluginError.