Gate an optional effect at the shared primitive

An optional decorative surface treatment — a blur, a refraction, a glow, anything the user can switch off — has three parts: a stored preference, a way for the UI to read it, and the draw code. Only the third one is shared. Wire the gate to the third one.

// adapted — one local, published by the app theme, default ON
val LocalDecorEnabled = staticCompositionLocalOf { true }

// inside AppTheme(…, decorEnabled: Boolean = true, …)
CompositionLocalProvider(
    LocalDecorEnabled provides decorEnabled,
    /* the theme's other locals */
    content = content,
)