Fix the Show keys toggle: flip the real paused state

ToggleSwitch does not flip checked on click — it only emits toggled()
and the caller owns the value. Reading !checked there yielded the
current bound state, so setPaused's guard always early-returned and the
toggle never did anything. Flip !root.paused instead; the checked
binding follows the flag file.

manifest.json

@@ -2,7 +2,7 @@
   "schemaVersion": 1,
   "id": "felixzsh.key-visualizer",
   "name": "Key Visualizer",
-  "version": "1.3.1",
+  "version": "1.3.2",
   "description": "Shows the keys you press on screen. Great for keybinding tutorials, demos, and screencasts.",
   "kinds": [
     "panel",