Document the launch OSD flag where it lives

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

shell/services/AppLibrary.qml

@@ -26,6 +26,9 @@ Item {
   property int launchSerial: 0
   property int launchToplevelCount: 0
   property var launchActiveToplevel: null
+  // True while the launch OSD is on screen. It outlives the launch that opened
+  // it: the OSD shows with duration 0, so only closeLaunchFeedback() takes it
+  // down.
   property bool launchOsdOpen: false
   property string launchOsdMessage: ""
 
@@ -150,11 +153,6 @@ Item {
     try { return ToplevelManager.toplevels.values.length } catch (e) { return 0 }
   }
 
-  // launchOsdOpen tracks whether the OSD is on screen, not which launch put it
-  // there, so a new launch must not clear it: the OSD is shown with duration 0,
-  // and only closeLaunchFeedback() takes it down. Dropping the flag here would
-  // orphan an OSD left over from the previous launch, and the timer restarts
-  // below discard the timeout that was its last chance to close.
   function beginLaunchFeedback(name) {
     root.launchSerial++
     root.launchToplevelCount = root.toplevelCount()