Show the cluster's solar weather in a bandmap status bar

The reader follows N1MM's rules for WWV and WCY lines and the sh/wwv
table. The bar is hidden until the cluster has sent some.

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

src/Nonemm.App/AppSession.cs

@@ -914,6 +914,7 @@ public sealed partial class AppSession : IDisposable
     public void ConnectCluster()
     {
         cluster?.Dispose();
+        SetSolar("");
         cluster = new ClusterClient(
             Settings.ClusterHost,
             Settings.ClusterPort,
@@ -923,14 +924,28 @@ public sealed partial class AppSession : IDisposable
             autoLogon: Settings.ClusterAutoLogon,
             keepAliveInterval: TimeSpan.FromMinutes(Math.Max(1, Settings.ClusterKeepAliveMinutes)));
         cluster.SpotArrived += (_, spot) => TakeSpot(spot);
+        cluster.SolarArrived += (_, text) => SetSolar(text);
         cluster.ConnectionChanged += (_, _) => Changed?.Invoke(this, EventArgs.Empty);
         cluster.Start();
     }
 
+    /// The latest solar weather the cluster sent, or empty when it has sent
+    /// none on this connection.
+    public string Solar { get; private set; } = "";
+
+    public event EventHandler? SolarChanged;
+
+    private void SetSolar(string text)
+    {
+        Solar = text;
+        SolarChanged?.Invoke(this, EventArgs.Empty);
+    }
+
     public void DisconnectCluster()
     {
         cluster?.Dispose();
         cluster = null;
+        SetSolar("");
         Changed?.Invoke(this, EventArgs.Empty);
     }