Say what the serial number messages do

The README and the comments said the pool "goes out" and named it in
places where the reader cannot tell what is sent. They now name the
message and what it holds: the highest number taken on each band.

One of them was also wrong. The pool has not been sent on a reset since
the reset started counting from the log, and the README still said it was.

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

src/Nonemm.App/AppSession.cs

@@ -234,9 +234,9 @@ public sealed class AppSession : IDisposable
         // the other stations refuse to resynchronise with a station on another
         // contest, and say so, which is only any use if they are told
         _ = link?.SendContestNameAsync();
-        // and where this station's serial numbers have got to, so a station
-        // joining a contest already under way counts from the same place.
-        // N1MM sends the pool at the same point
+        // and the highest serial number taken on each band, so a station that
+        // joins a contest already under way starts where the others are. N1MM
+        // sends the same message at the same point
         _ = link?.SendSerialNumbersAsync(Logging.Numbers.Snapshot());
         Logging.Changed += (_, _) => Changed?.Invoke(this, EventArgs.Empty);
         Logging.Logged += (_, qso) =>
@@ -413,8 +413,8 @@ public sealed class AppSession : IDisposable
 
     /// Starts the serial numbers again from the log: the next number becomes
     /// the highest one in it plus one. The contacts already logged keep the
-    /// numbers they were sent with. N1MM sends no pool with this — every
-    /// station works the same number out of its own copy of the log.
+    /// numbers they were sent with. Nothing is sent but `RESETQSONRS`, as in
+    /// N1MM: each station works the same number out of its own copy of the log.
     public void ResetSerialNumbers()
     {
         if (Logging is not null)
@@ -425,9 +425,10 @@ public sealed class AppSession : IDisposable
     }
 
     /// A serial number another station has taken. It is noted here so this
-    /// station counts past it. A number at or below what this station has
-    /// already used says the other one is behind, and the whole pool goes back
-    /// so it can catch up, which is what N1MM answers with.
+    /// station counts past it. A number at or below one this station has
+    /// already used says the sender is behind, and it is sent the highest
+    /// number for each band so it can count on from the right one, which is
+    /// what N1MM answers with.
     private void TakeReservedNumber(ReservedNumberMessage taken)
     {
         if (Logging is not { } logging)