On-demand dictionary asset

A ~13 MB Japanese tokenizer dictionary (eight .bin files) is worth excluding from the Android APK and fetching on demand; the same code on desktop keeps shipping it on the classpath, because a desktop install is not counted in megabytes the same way. One expect/actual seam carries the whole feature across that split:

// adapted — each function's KDoc is elided; the three signatures are verbatim
expect object RomanizationDictionaryPack {
    fun configure(directoryPath: String)
    fun isReady(): Boolean
    suspend fun download(): Result<Unit>
}