Gaze first: abandoned; keep the controller experiment for reference

The last state of the experiment, kept on this branch only:
- input/gazefirst.py, input/steamui.py: the relay reading the controllers from
  vrserver's web socket, switching the compositor binding, and driving the Steam
  UI filter (whose block now expires unless renewed).
- The helper's trigger and bumper holds (steered by the controller's position),
  the laser keeper, and the click gate that waits for the laser.
- pointer/probe/focustest (overlay flag 1 << 4, as an input client too),
  vrsetting (SteamVR settings through vrserver), lasertest --reclaim.

Every press and release Steam sees takes SteamVR out of laser mode, and taking
the laser back breaks clicks and drags. See docs/gaze-controllers.md on
experimental.

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

pointer/probe/focustest_actions/bindings_frame_controller.json

@@ -0,0 +1,15 @@
+{
+	"action_manifest_version": 0,
+	"controller_type": "frame_controller",
+	"description": "focustest (pointer/probe/focustest.cpp)",
+	"name": "focustest",
+	"bindings": {
+		"/actions/focus": {
+			"sources": [
+				{"path": "/user/hand/right/input/y", "mode": "button", "inputs": {"click": {"output": "/actions/focus/in/y"}}},
+				{"path": "/user/hand/right/input/trigger", "mode": "button", "inputs": {"click": {"output": "/actions/focus/in/trigger"}}},
+				{"path": "/user/hand/left/input/trigger", "mode": "button", "inputs": {"click": {"output": "/actions/focus/in/trigger"}}}
+			]
+		}
+	}
+}