Ripple: one alpha lever, and bounds you owe by hand

The theme publishes one configuration and every touchable surface picks it up. Two things are worth changing there, and only one of them is safe to change.

// adapted — provided once at the top of the theme, alongside the colour scheme
CompositionLocalProvider(
    LocalRippleConfiguration provides SoftRippleConfiguration,
    LocalContentColor provides colorScheme.onSurfaceVariant,
    …
) { content() }