Pause Frametop for VR games

Frametop kept using the headset during games: with gaze mode off, our eye tracker still took
about 60% of a core, remote desktop about 2 cores while on, and KWin kept drawing hidden
screens because ft-screens sent their frame callbacks at 90 Hz. Pausing gives that back, and
resuming brings back only what pausing stopped. It's also a way to keep the gaze service and
our eye tracker off during games, which PR #13 asked for.

Paused (input/game_pause.py, run by the input relay):
- frametop-gaze stops (ft-eyegrab then idles by itself), and hand tracking and remote desktop
  stop if they run
- the desktop hides and slows down: ft-screens "pause on" hides every panel and sends KWin a
  frame callback once a second; or, with pause_desktop "close", the desktop closes and starts
  again on resume
- the relay lets go of the 3D mouse, typing goes to Steam, and mapped buttons and key
  combinations do only pause_toggle, steam_menu and commands

Toggled by both thumbsticks clicked together twice (configurable), read passively from
vrserver's web socket (input/vrws.py) so it works in games and takes nothing from them; by the
new pause_toggle action; by input/ft-pause; and, with pause_auto (default on), by a VR game
starting and ending, which the pointer helper now reports ("vrgame 1|0"). Frametop Input
Settings has a Games page for it. update-check.py checks the web socket, and doesn't count a
paused gaze service as failed.

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

input/ft-pause

@@ -0,0 +1,45 @@
+#!/usr/bin/python3
+"""ft-pause: pause Frametop for a VR game, so it leaves the CPU and GPU to the game, or resume it.
+
+  ft-pause on|off|toggle   pause or resume (input/game_pause.py has what pausing stops)
+  ft-pause status          the pause state, as JSON (the default)
+
+The input relay does it (frametop-input-relay.service). So do the pause_toggle action, the
+controller gesture (by default both thumbsticks clicked together twice), and, with auto pause on,
+a VR game starting; Frametop Input Settings has the settings, on its Games page.
+"""
+
+import json
+import os
+import socket
+import sys
+
+
+def ask(msg, timeout=2.0):
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM | socket.SOCK_CLOEXEC)
+    s.bind(f"\0ft_pause.{os.getpid()}")
+    s.settimeout(timeout)
+    try:
+        s.sendto(msg.encode(), "\0frametop_relay")
+        return json.loads(s.recv(65536))
+    except ConnectionRefusedError:
+        sys.exit("the input relay isn't running (frametop-input-relay.service)")
+    except (socket.timeout, ValueError):
+        sys.exit("no answer from the input relay (an older one, without pausing?)")
+    finally:
+        s.close()
+
+
+def main():
+    cmd = sys.argv[1] if len(sys.argv) > 1 else "status"
+    if cmd in ("on", "off", "toggle"):
+        r = ask(f"pause {cmd} command")
+        print("Frametop paused" if r.get("paused") else "Frametop running")
+    elif cmd == "status":
+        print(json.dumps(ask("pause ?"), indent=1))
+    else:
+        sys.exit(__doc__)
+
+
+if __name__ == "__main__":
+    main()