`AdvancedPicker` is the one leaf on the converter screen that carries its own
state, and `ValidationError` is deliberately invoked after the
`AnimatedVisibility` that gates the chip rows -- so an invalid spec explains
itself and offers one-tap fixes while the section is collapsed. That is the
only route out of an invalid spec for a user who never opened Advanced, it was
completely untested, and folding the two `if` blocks into one is a plausible
tidy-up that compiles.
`AdvancedPickerTest` covers the gate in both directions, clicks each of the
four colliding chip labels through its own row tag, and does every assertion
about the error card with the toggle untouched.
`AdvancedPanelSavedStateTest` is the `DestinationSaverTest` split for
`expanded`: `StateRestorationTester` saves into an in-memory map, so it proves
`rememberSaveable` is in use and nothing about the representation. Driving a
real `SaveableStateRegistry` shows the picker saves the `MutableState` itself
rather than the `Boolean`, which only survives a rotation because
`mutableStateOf` on Android returns a `Parcelable` one.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
JMR-dev
