Write what N1MM needs before it will open a log

Checked by opening a log this program wrote in N1MM 1.0.11031. Three things it
rejected:

- a log naming a contest with no row in the Contest table throws "No current
  row" in Contest.FromRow, so the definition row is written whenever a contest
  is opened;
- an empty overlay category is answered with "Invalid Overlay Category:", so an
  entry with no overlay now says "N/A", and the dialog offers N1MM's list;
- the sent exchange omits the report, which is what N1MM's own contest dialog
  asks for.

With those three fixed N1MM opens the log and shows the contacts.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.Contests/Rules/ArrlDx.cs

@@ -35,9 +35,7 @@ public sealed class ArrlDx : Contest
     public IReadOnlyList<ModeCategory> Modes => [mode];
 
     public string SentExchangeFor(StationInfo me) =>
-        IsNorthAmericanHome(me)
-            ? $"{DefaultReport()} {StateOrProvince(me)}"
-            : $"{DefaultReport()} {me.Power}";
+        IsNorthAmericanHome(me) ? StateOrProvince(me) : me.Power;
 
     /// Only contacts across the W/VE line count, so a DX station working DX or
     /// a W station working W scores nothing.
@@ -88,5 +86,4 @@ public sealed class ArrlDx : Contest
 
     private string ModeLabel() => mode == ModeCategory.Cw ? "CW" : "SSB";
 
-    private string DefaultReport() => mode == ModeCategory.Cw ? "599" : "59";
 }