Send the messages N1MM actually reads

Three of the messages this program sends were its own invention or in the
wrong units, so an N1MM beside it read them wrongly or not at all.

| Message | N1MM | What was sent |
|---|---|---|
| `XMIT` | transmitting, the function key's caption, Run2, F1 pressed, stop sending | transmitting, the radio number |
| `PASSFREQ` | the frequency in hundredths of a kilohertz, and nothing else | the frequency in kilohertz, and a callsign |
| `FREQ` | the frequency in hundredths of a kilohertz | `BANDMAP`, which N1MM has no such message for |

So N1MM showed a radio number where the other operators read what a
station is sending, read a pass on 14205.5 as 140.25, and never saw this
station move at all. `BANDMAP` is gone: the frequency goes out in `FREQ`
when the radio moves and the mode, run and the rest ride in the `STATUS`
that follows it, which is where N1MM carries them.

The `Msg` column now shows what a station is sending, which is what the
caption is for. `PassCall` and `RadioNumber` are gone from the station:
neither is on the wire, so neither was ever anything but this program
talking to itself.

**A station that reconnects resynchronises by itself.** N1MM sends
`LASTQAT` — when I last worked anybody — as soon as a connection opens,
and a station holding nothing that late asks for the hours in between. An
empty log asks for nothing: a program that has just been started has no
business pulling the whole contest across, and N1MM suppresses it the same
way. The answer goes over the connection this station opens, which is not
always up when the message arrives, so a resync that has nothing to ask
over waits for it rather than being lost — and one that still cannot send
stops and says so instead of leaving the row resynchronising for the rest
of the contest.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PdAYHcdRktqKry7nk414TU

src/Nonemm.App/AppSession.cs

@@ -344,7 +344,9 @@ public sealed class AppSession : IDisposable
         Changed?.Invoke(this, EventArgs.Empty);
     }
 
-    /// Tells the other stations where this one is, if it has moved. In a
+    /// Tells the other stations where this one is, if it has moved. The
+    /// frequency goes out on its own — N1MM's `FREQ` — and everything else
+    /// about the position rides in the `STATUS` that follows it. In a
     /// multi-single entry this is what the other operators watch: two stations
     /// on one band is a contact nobody can make.
     private void AnnounceWhereIAm()
@@ -359,8 +361,15 @@ public sealed class AppSession : IDisposable
         {
             return;
         }
+        bool moved = announced.Where != position.Frequency;
         announced = now;
-        _ = link.SendBandAsync(position.Frequency, position.Mode, position.IsRunning, position.RadioNumber);
+        if (moved)
+        {
+            _ = link.SendFrequencyAsync(position.Frequency);
+        }
+        // the mode, run and the rest of it ride in `STATUS`, which is sent
+        // again now rather than waiting out the rest of its interval
+        statusSent = default;
     }
 
     /// Scores the log again and writes the points and multiplier flags from