Gaze first: test results; treadmill from the start, muted compositor binding

From the first headset tests (docs/gaze-first.md, "Test results"):
- SteamVR gives the treadmill path only to a device that hints it when
  it's added, so the driver hints a role that's no hand from Activate
  (a hand still only while shown). With it, our device held the
  dashboard laser with no hand role. The helper doesn't release the
  pointer for having no hand role when POINTER_ROLE is treadmill.
- The helper's global action sets can't mute the compositor (SteamVR
  reports them inactive while the laser mouse has focus), but selecting
  pointer/bindings/vrcompositor_frame_controller_gazefirst.json (the
  stock binding without its trigger and bumper laser entries) through
  vrserver's /input/selectconfig.action does.
- input/vrws.py follows devices that connect later.

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

pointer/helper/ft-pointer.cpp

@@ -1353,8 +1353,9 @@ int main() {
             if (debug) std::fflush(stdout);
         }
 
-        // Didn't get the hand role (a held controller keeps it): release, back off.
-        if (active && tnow - wokeAt > std::chrono::seconds(1) && ours != vr::k_unTrackedDeviceIndexInvalid &&
+        // Didn't get the hand role (a held controller keeps it): release, back off. Treadmill is
+        // no hand, and SteamVR reports no role for it (it's /user/treadmill): nothing to lose.
+        if (active && role != "treadmill" && tnow - wokeAt > std::chrono::seconds(1) && ours != vr::k_unTrackedDeviceIndexInvalid &&
             sys->GetControllerRoleForTrackedDeviceIndex(ours) == vr::TrackedControllerRole_Invalid) {
             active = false;
             claimPending = claimHeld = false;