Move the head-follow cursor only after the head passes the leash

Easing the reference toward the head all the time moved the cursor on
every small head movement, so a cursor parked in a corner of the view
drifted. Now nothing moves while the head stays within the leash. Once
the head has been past it for POINTER_LEASH_DELAY (0.2 s, so a glance
out and back doesn't count), the reference eases all the way to where
you face (POINTER_LEASH_RETURN) and the cursor lands back in its place
in the view, then the leash waits again. Leaning inside the leash no
longer moves the cursor either. Leash 0 stays head-locked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -53,7 +53,7 @@ If you work in the desktop for long stretches, stop Steam from putting the heads
 | Meta+Shift+H in the desktop | Hides or shows all screens (also in the menu as Hide/Show Screens, and mappable). The Visibility & wrist tab of Frametop Display Settings can instead show them only with the dashboard open, or while you look at your wrist |
 | Play a VR game | The screens hide and your controllers stay in the game. Open the SteamVR dashboard, or press Meta+Shift+H, to see and use them. To keep them visible over games, change During VR games on the Visibility & wrist tab; the controllers still stay in the game, and you use the screens with the mouse or the dashboard |
 
-You can map the mouse's extra buttons to actions such as Toggle SteamVR dashboard, Recenter pointer, or Head follow on/off on the Buttons page of Frametop Input Settings. Pointer speed, dot size, and the rest are on its Pointer page and take effect immediately. Head follow, off by default, makes the pointer come along when you turn your head: small head movements barely move it, it settles back to its place in your view when your head stops, and a leash of 0 keeps it fixed in your view.
+You can map the mouse's extra buttons to actions such as Toggle SteamVR dashboard, Recenter pointer, or Head follow on/off on the Buttons page of Frametop Input Settings. Pointer speed, dot size, and the rest are on its Pointer page and take effect immediately. Head follow, off by default, makes the pointer come along when you turn your head: it stays put until your head turns past the leash angle, then glides back to its place in your view, and a leash of 0 keeps it fixed in your view.
 
 Restarting the desktop (Restart desktop in Frametop Display Settings) closes its windows, but background work you started in it, such as servers, tmux sessions, or builds, keeps running.