Close button quits app instead of hiding to tray

- OnFormClosing no longer intercepts close button — app quits on X
- Minimize still hides to tray (OnResize unchanged)
- Removed unused _closingFromTray flag
- Tray Exit and tray double-click restore unchanged

MainForm.cs

@@ -21,8 +21,6 @@ public class MainForm : Form
     readonly System.Windows.Forms.Timer _statusTimer;
     readonly CancellationTokenSource _loopCts;
 
-    bool _closingFromTray;
-
     readonly HeatMap _heatA;
     readonly HeatMap _heatB;
     readonly ProgressBar _gaugeRecvA;
@@ -377,7 +375,6 @@ public class MainForm : Form
 
     void ExitFromTray()
     {
-        _closingFromTray = true;
         _tray.Visible = false;
         Application.Exit();
     }
@@ -390,12 +387,6 @@ public class MainForm : Form
 
     void OnFormClosing(object? sender, FormClosingEventArgs e)
     {
-        if (e.CloseReason == CloseReason.UserClosing && !_closingFromTray)
-        {
-            e.Cancel = true;
-            Hide();
-            return;
-        }
         _tray.Visible = false;
         _statusTimer.Stop();
         _loopCts.Cancel();