Add a hints example to the homepage and simplify the hint-to-tour docs

The homepage examples grid gains a Hints button that toggles three
beacons on the hero: one plain dismissable hint, one whose button starts
a short tour through onButtonClick (showing the two features hand off to
each other), and one whose button leads to the hints guide. The last-row
label shrinks from 'and much more ...' to 'and more ...' so the row
keeps to one line.

The guide's hint-launches-tour example now uses buttonText plus
onButtonClick instead of hand-building a button in onPopoverRender,
which stays mentioned for additional buttons.