Shorten the bandmap hover text to frequency, spotter, age and comment

The first line reads "14025.0 by K1TTT, 41m ago". The comment follows
on a second line and is left out when it is only LSB, USB or SSB.
Control characters are removed from the comment: cluster lines end in
bell and carriage-return characters, which the tooltip drew as boxes.

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

src/Nonemm.Spotting/SpotDescription.cs

@@ -2,23 +2,38 @@ using System.Globalization;
 
 namespace Nonemm.Spotting;
 
-/// What the bandmap shows when the pointer rests on a spot: who spotted it,
-/// when, and the comment they sent.
+/// What the bandmap shows when the pointer rests on a spot: the frequency,
+/// who spotted it and how long ago, and the comment if it says more than the
+/// sideband.
 public static class SpotDescription
 {
-    public static string Of(Spot spot)
+    public static string Of(Spot spot, DateTime? nowUtc = null)
     {
-        string time = spot.AtUtc.ToString("HH:mm", CultureInfo.InvariantCulture);
+        string age = Age((nowUtc ?? DateTime.UtcNow) - spot.AtUtc);
         string kilohertz = spot.Frequency.Kilohertz.ToString("0.0", CultureInfo.InvariantCulture);
-        string who = spot.Spotter.Length > 0
-            ? $"Spotted by {spot.Spotter} at {time}Z"
-            : spot.Source switch
-            {
-                SpotSource.Log => $"Worked at {time}Z",
-                SpotSource.Operator => $"Spotted here at {time}Z",
-                _ => $"Spotted at {time}Z",
-            };
-        string text = $"{spot.Call.Text}  {kilohertz}\n{who}";
-        return spot.Comment.Trim().Length > 0 ? $"{text}\n{spot.Comment.Trim()}" : text;
+        string first = spot.Spotter.Length > 0
+            ? $"{kilohertz} by {spot.Spotter}, {age}"
+            : $"{kilohertz}, {age}";
+        string comment = Comment(spot.Comment);
+        return comment.Length > 0 ? $"{first}\n{comment}" : first;
+    }
+
+    private static string Age(TimeSpan span)
+    {
+        int minutes = Math.Max(0, (int)span.TotalMinutes);
+        return minutes switch
+        {
+            < 60 => $"{minutes}m ago",
+            _ => $"{minutes / 60}h {minutes % 60}m ago",
+        };
+    }
+
+    /// Cluster lines end in bell and carriage-return characters, which a
+    /// tooltip draws as boxes, so control characters are dropped.
+    private static string Comment(string text)
+    {
+        string clean = new([.. text.Where(c => !char.IsControl(c))]);
+        clean = clean.Trim();
+        return clean.ToUpperInvariant() is "LSB" or "USB" or "SSB" ? "" : clean;
     }
 }