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.Network/StationLink.cs

@@ -443,8 +443,8 @@ public sealed class StationLink : IDisposable
             StationMessages.ReserveNumber(number, frequency, StationNumber, computerName),
             cancellation);
 
-    /// Sends the whole pool, which is what a station answers with when the
-    /// number another one has taken is one this station has already used.
+    /// Sends the highest serial number taken on each band, which is the answer
+    /// to a station that has claimed a number this one has already used.
     public Task<int> SendSerialNumbersAsync(
         IReadOnlyList<int> numbers,
         CancellationToken cancellation = default) =>