[Windows] Wacom pen uses all screens but only in Photoshop (how to fix)

I was just bitten by this and thought I'd share how to fix it since I couldn't find anything on Google.

You have multiple screens and have constrained your Wacom tablet/pen to just one of them, but when (and only when) Photoshop is the active window, the pen uses all screens.

This is due to a boneheaded feature of the Wacom driver. Open "Wacom Tablet Properties" and notice that the "Applications" section of the interface lists Photoshop as an entirely separate app. Here you can instruct it to use the screen you want (and optionally disable use of Windows Ink since that "feature" has only ever done more harm than good).

Why Wacom thought it would be a good idea to do this without telling anyone I have no idea.