Keep an excluded contact out of the score the way N1MM does

Three things were wrong with a contact the operator takes out of the claimed
score. The decompiled reference gives the rule in four places:

- `Contest.cs:437` returns zero points when `IsClaimedQso` is 0.
- `ContestInstance.cs:307` builds the where clause `CLAIMEDQSO = 1`, which the
  dupe search (`DBSupport.cs:1189`) and the multiplier search
  (`DBSupport.cs:1327`) both use, so an unclaimed contact takes nothing away
  from a later one.
- The score query (`DBSupport.cs:1807`) adds `ContactType <> 'D'`, which the
  other two do not. A contact marked as a dupe is therefore still searched for
  dupes and multipliers, and is left out of the score alone.
- `Contact.cs:1563`, `3307` and `3881` write `X-QSO:` rather than dropping the
  contact from the Cabrillo file.

`ContestLog` scored an unclaimed contact in full, and the Cabrillo writer left
it out of the file. `Qso.IsInScore` now holds the score rule and
`StatisticsPivot` uses it instead of its own copy.

The same reference also fixes the sent serial in three Cabrillo exporters.
ARRL 10M, Ukrainian DX and YO DX HF formatted the sent exchange from the
station rather than the contact, so a DX entrant exported `001` on every line.
N1MM reads the contact's own number: `CArrl10m.cs:122` writes it unpadded,
`CUkrainian.cs:232` and `CYOHFDX.cs:167` pad it to three digits.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015NZkFxHde1iifAQemFTHxf

src/Nonemm.Contests/ContestLog.cs

@@ -47,6 +47,10 @@ public sealed class ContestLog
     /// What logging this contact right now would do, without logging it.
     public Verdict Judge(Qso candidate)
     {
+        if (!candidate.IsClaimed)
+        {
+            return new Verdict(false, 0, []);
+        }
         QsoContext context = ContextFor(candidate);
         if (!contest.IsContact(candidate))
         {
@@ -164,9 +168,23 @@ public sealed class ContestLog
         IsMultiplier3 = claimed.Any(m => m.Index == 3),
     };
 
+    /// Adds the contact to the score and to the indexes that answer "worked
+    /// before?" and "new multiplier?". An unclaimed contact enters neither:
+    /// N1MM scores it as zero and leaves it out of both searches, so it takes
+    /// nothing away from a later contact with the same call or multiplier. A
+    /// contact marked as a dupe is the other way round — N1MM searches for
+    /// dupes and multipliers among it, and leaves it out of the score alone.
     private void Index(Qso qso, Verdict verdict)
     {
-        tally.AddQso(verdict.Points);
+        if (!qso.IsClaimed)
+        {
+            return;
+        }
+        bool counts = qso.IsInScore;
+        if (counts)
+        {
+            tally.AddQso(verdict.Points);
+        }
         if (!contest.IsContact(qso))
         {
             return;
@@ -175,7 +193,10 @@ public sealed class ContestLog
         foreach (Multiplier multiplier in verdict.NewMultipliers)
         {
             claimedMultipliers.Add(MultiplierKey(multiplier, qso));
-            tally.AddMultiplier(multiplier);
+            if (counts)
+            {
+                tally.AddMultiplier(multiplier);
+            }
         }
     }