Add a Linger NumberField to the menu

Native qs.Ui.NumberField (SpinBox) for lingerMs: mouse wheel, +/- buttons
and typing, 0-10000ms in 500ms steps, writing config.json like Mode and
Position so the display updates live. 0 selects the always-show behavior
from the previous commit.

Panel.qml

@@ -219,6 +219,19 @@ Panel {
         ]
         onChanged: function(v) { root.writeConfig({ position: v }) }
       }
+
+      // Linger --------------------------------------------------------
+      NumberField {
+        id: lingerField
+        width: parent.width
+        label: "Linger"
+        value: root.lingerMs
+        from: 0
+        to: 10000
+        stepSize: 500
+        // 0 = always show (keep the last combo until the next key).
+        onModified: function(v) { root.writeConfig({ lingerMs: v }) }
+      }
     }
   }
 }

README.md

@@ -65,6 +65,9 @@ menu, following the native bar-widget pattern:
 - **Mode** — `All keys` or `Bindings only` (only combos with a modifier).
 - **Position** — a dropdown with all nine placements (top/middle/bottom
   × left/center/right) of the screen.
+- **Linger** — a numeric field (wheel, +/− buttons, or typing) for how long
+  a released combo stays, 0–10s in 500ms steps; `0` keeps the last combo on
+  screen until the next key.
 
 The menu writes the same pause flag and `config.json` that the display
 panel watches, so it stays in sync across monitors. You can also drive it

manifest.json

@@ -2,7 +2,7 @@
   "schemaVersion": 1,
   "id": "felixzsh.key-visualizer",
   "name": "Key Visualizer",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "Shows the keys you press on screen. Great for keybinding tutorials, demos, and screencasts.",
   "kinds": [
     "panel",