Variable
ConstDeliberately not a SafariInstallStep. The learner acts on nothing
here, so it carries no targetKey, and counting it as another step would
overstate how much work the flow takes. A guide that stops at the
confirmation asks for taps and never shows what they were for.
A Mac has no home screen, which is why the two differ: one ends on the home screen and the other in the Dock.
Where the icon comes to rest on each platform.