VR keyboard swipe: only the pressing controller's laser builds the path

With both controllers on the keyboard, the idle one's hover (mouse events,
pointerId 1) arrived during the other's press and went into the swipe path
("tust" for "test"). A gesture now belongs to the contact that started it
(touch identifier, pointerId or mouse; gesture-input.js): other contacts'
moves, releases and cancels are ignored, a second press meanwhile stays
Steam's tap. Test with a recorded two-controller swipe.

modules/vr-keyboard.nix

@@ -1,6 +1,7 @@
 # Swipe typing, suggestions and a Backspace drag for Steam's VR keyboard
 # (steamFrame.keyboard.vr; the extra keys are vr-keyboard-extra-keys.nix).
-# - vr-keyboard/patch.js (Steam UI, 8080): swipe gestures (swipe-decoder.js),
+# - vr-keyboard/patch.js (Steam UI, 8080): swipe gestures (swipe-decoder.js;
+#   gesture-input.js: the events of the laser that pressed),
 #   a model of what the keyboard typed (textmodel.js), suggestions (swipe
 #   alternatives, corrections and completions, corrector.js; never changing
 #   text by themselves), Backspace drag (left: delete with a detent at word
@@ -55,7 +56,7 @@ let
         inherit (cfg.backspaceDrag) wordDetentPixels;
         inherit (cfg) haptics;
       };
-      extraArgs = [ ./vr-keyboard/swipe-decoder.js ./vr-keyboard/textmodel.js ./vr-keyboard/corrector.js dictionaryJs ];
+      extraArgs = [ ./vr-keyboard/swipe-decoder.js ./vr-keyboard/textmodel.js ./vr-keyboard/corrector.js dictionaryJs ./vr-keyboard/gesture-input.js ];
     }} $out
     node --check $out
   '';