Constant EVENT_EDITOR_FILE_CHANGED 

pub const EVENT_EDITOR_FILE_CHANGED: &str = "editor:file_changed";

MPS event fired when a file open in at least one editor tab changes on disk. Scoped per-block (block:<id>) via MuxEvent::scopes, matching EVENT_CONTROLLER_STATUS/EVENT_BLOCK_ACTIVITY’s existing pattern — never a global broadcast, so panes on unrelated files aren’t notified. Payload is deliberately just the path (a wake signal, not content); the frontend re-fetches via the existing readeditorfile RPC.