Mark the CQ frequency on the bandmap and leave Run when the radio moves off it

Starting Run stores the frequency in the position. The bandmap draws a
purple, bold "CQ Frequency" pseudospot there, which is not added to the
shared bandmap, and a click on it tunes back and sets Run. A move of more
than 3 kHz (a setting on the telnet Filters tab) while running switches
to search and pounce.

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

src/Nonemm.Spotting/Spot.cs

@@ -43,6 +43,17 @@ public sealed record Spot(
     /// opposed to one from the cluster.
     public bool IsLocal => Source == SpotSource.Operator && IsStation;
 
+    /// The pseudospot that marks where the operator is running. It is drawn on
+    /// the bandmap and is never added to it.
+    public bool IsCqFrequency { get; init; }
+
+    public static Spot CqFrequency(Frequency where, DateTime atUtc) =>
+        new(Callsign.Parse("CQ Frequency"), where, atUtc, SpotSource.Operator)
+        {
+            IsStation = false,
+            IsCqFrequency = true,
+        };
+
     public bool IsSplit => Qsx.Hertz > 0;
 
     public Band? Band => Bands.ForFrequency(Frequency);