Calibration all in the headset panel; the gaze probe is a development tool

Check headset fit now runs in the headset panel too ("fitcheck"): a card per
eye (tracked or lost, the tracker's signal, how much of the last 10 s it was
seen) and the hints, from the probe's fitcheck.py, updated at most twice a
second; left click or Meta+J runs its guided check, right click or Meta+K closes
it. So Quick check, Calibrate, and Check headset fit all happen in one place.

The gaze probe moves to the Gaze page's overflow menu as "Gaze probe
(development)", and its app menu entry says it's a development tool. Texts that
sent users to it ("use Calibrate… with Own tracker") point at Calibrate.

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

gaze/probe/ft-gazeprobe.desktop

@@ -1,9 +1,9 @@
 [Desktop Entry]
 Type=Application
-Name=Frametop Gaze Probe
-GenericName=Eye tracking playground
-Comment=How accurate the headset's eye tracking is on your screens, and gaze clicking with calibration
+Name=Frametop Gaze Probe (development)
+GenericName=Eye tracking development tool
+Comment=For developing Frametop's gaze tracking. Day to day, the calibration and checks are on the Gaze page of Frametop Input Settings
 Exec=@REPO@/gaze/probe/ft-gazeprobe
 Icon=view-visible
-Categories=Utility;Development;
+Categories=Development;
 Keywords=eye;gaze;tracking;calibration;pointer;steamvr;frametop;