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/check.nix

@@ -1,6 +1,7 @@
 # Tests of the VR keyboard (flake check `vr-keyboard`, also built before the
 # patch by vr-keyboard.nix with the configured dictionary): text model,
-# corrector and swipe-decoder accuracy (tests/*.test.mjs). The accuracy
+# gesture input (two controllers), corrector and swipe-decoder accuracy
+# (tests/*.test.mjs). The accuracy
 # thresholds (German keyboard geometry, German and English words) fail the
 # build only for German + English dictionaries, the default here.
 { pkgs
@@ -20,6 +21,7 @@ in
 pkgs.runCommand "vr-keyboard-checks" { nativeBuildInputs = [ pkgs.nodejs ]; } ''
   set -o pipefail
   node ${./tests/textmodel.test.mjs} ${./textmodel.js}
+  node ${./tests/gesture-input.test.mjs} ${./gesture-input.js} ${./tests/two-controllers.json}
   node ${./tests/corrector.test.mjs} ${./corrector.js} ${./swipe-decoder.js} ${words} ${lib.optionalString (!strict) "|| echo warning: corrector test failed"}
   node ${./tests/swipe-decoder.test.mjs} ${./swipe-decoder.js} ${words} 100 1 | tee $out ${lib.optionalString (!strict) "|| true"}
   node -e '