Map the Frame controllers' buttons; make gaze clicks correctable

The Frame controllers aren't input devices on the host, so the pointer
helper reads them with SteamVR input (vrbuttons.h, actions/), one action
set per button, and sends presses to the relay, which does the mapped
action like for a mouse button. Only mapped buttons are taken, at an
overlay-global priority (SteamVR's experimental "Enable global input from
overlays"), and only outside games unless In games is on. Frametop Input
Settings gets a Controllers page to map them.

Gaze mode: a left press while the gaze has the pointer isn't sent at
once. The pointer stops, you drag it onto what you meant with the button
held, and the release clicks there; a press held still for
POINTER_GAZE_HOLD (0.5 s) becomes a real press, for drags. The dot shows
only while the mouse moves it (POINTER_GAZE_SHOW), while a press is held,
and as a pulse per click. Outside games the pointer stays on while gaze
mode is on. ft-gazed takes a third of each lesson's offset instead of all
of it: in the first live test one 6 degree lesson moved everything and put
the next target 7 degrees off. Frametop Input Settings gets a Gaze page.

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

session/frametop.conf.example

@@ -26,6 +26,8 @@ POINTER_FOLLOW_REACH=70    # head follow: how far (degrees) from the middle of y
 POINTER_GAZE=0             # 1 = the pointer goes where you look, the mouse does the last bit (needs the gaze service: gaze/run.sh install)
 POINTER_GAZE_RETAKE=5      # gaze mode: how far (degrees) you look away from the pointer before the gaze takes it back from the mouse
 POINTER_GAZE_NUDGE_MAX=8   # gaze mode: a mouse nudge up to this far (degrees) before a click is learned as the eye tracker's error
+POINTER_GAZE_HOLD=0.5      # gaze mode: a press held this long (s) without moving becomes a real press (to drag); moved or released sooner, it clicks where you let go
+POINTER_GAZE_SHOW=1        # gaze mode: the dot shows this long (s) after the mouse moves it; also while a press is held, and a pulse per click
 META_DASHBOARD=0   # 1 = a Meta tap on a pass-through keyboard toggles the SteamVR dashboard (pointer mode only)
 SHARE_KEYS=0       # 1 = keys of keyboards grabbed for the desktop also go to @frametop_keys, for hotkey tools (any local process can listen)
 LAYOUT_GRAB_OFFSET=0.075   # arranging screens: where the floating window's grab bar is, in metres below the screen