IosFilePicker
iOS FilePicker. Calf's file-picker/file-saver launchers are @Composable — like IosDocumentScanner's VisionKit flow, they must be presented from live Compose UI, which this headless module has no hook into. Mirroring AndroidFilePicker, the host's Compose layer wires pickBridge/saveBridge to the real launchers; with no bridge registered this degrades to reporting no file, the same truthful-no-op fallback IosDocumentScanner uses.