Lay out a Cabrillo line the way a .udc file asks for it

`CabrilloString` names a field and a column width in turn. The line it makes
follows N1MM: the operator's callsign in the first 13 columns, then every
column padded to its width with one space after it, and a value longer than its
column cut rather than pushed sideways. The cut is new for every contest, not
just the user-defined ones — the columns are the sponsor's, not ours.

`CabrilloVersion` is read too, so a contest whose sponsor still asks for 2.0
gets it in the header.

A contest that lays out its own line can put the transmitter column where it
wants it, or leave it out, so the writer no longer adds one at the end.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RoGtneMQaz4M9w7Kk49AVD

src/Nonemm.Formats/Cabrillo/CabrilloWriter.cs

@@ -23,7 +23,7 @@ public sealed class CabrilloWriter
     public string Write(CabrilloHeader header, IEnumerable<Qso> qsos)
     {
         StringBuilder text = new();
-        text.Append("START-OF-LOG: 3.0\r\n");
+        text.Append("START-OF-LOG: ").Append(contest.CabrilloVersion).Append("\r\n");
         Line(text, "CONTEST", header.Contest);
         Line(text, "CALLSIGN", header.Callsign);
         Line(text, "CATEGORY-OPERATOR", header.OperatorCategory);
@@ -72,18 +72,23 @@ public sealed class CabrilloWriter
         line.Append(qso.TimestampUtc.ToString("HHmm", CultureInfo.InvariantCulture)).Append(' ');
         Append(line, exchange.Sent);
         Append(line, exchange.Received);
-        if (contest.IsContact(qso))
+        if (contest.IsContact(qso) && exchange.AddsTransmitter)
         {
             line.Append(qso.RadioNumber > 1 ? '1' : '0');
         }
         return line.ToString();
     }
 
+    /// Every column is the width the sponsor asks for and one space, and a
+    /// value longer than its column is cut, which is what N1MM writes.
     private static void Append(StringBuilder line, IReadOnlyList<CabrilloField> fields)
     {
         foreach (CabrilloField field in fields)
         {
-            line.Append(field.Value.PadRight(field.Width)).Append(' ');
+            string value = field.Value.Length > field.Width
+                ? field.Value[..field.Width]
+                : field.Value.PadRight(field.Width);
+            line.Append(value).Append(' ');
         }
     }