values() — list immediate children of a directory.
getDirectoryHandle(create) — create a directory.
getFile().text()/arrayBuffer() — read a file (base64 when binary).
removeEntry — delete a file or directory.
createWritable().write — write a file (data is base64 when binary).
Default when no fs handler is configured: lists nothing, reads empty, silently drops every write/mkdir/remove. Real persistence needs an FsResponder (HostFsRouter / ApiFsResponder / DiskFsResponder) via EditorBridgeHandlers.fs.