Add CW keying, function key messages and the documentation

The function keys send through cwdaemon or a WinKeyer, with N1MM's message
macros. Escape stops sending.

Settings are read with the reflection serializer rather than a generated one:
the generated one hands back null for every property the file leaves out
instead of the value the property is declared with, which crashed the program
the first time a new setting was added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.App/AppSession.cs

@@ -3,6 +3,7 @@ using Nonemm.Contests;
 using Nonemm.Core;
 using Nonemm.Core.Calls;
 using Nonemm.Core.Country;
+using Nonemm.Keying;
 using Nonemm.Network;
 using Nonemm.Rig;
 using Nonemm.Session;
@@ -20,6 +21,7 @@ public sealed class AppSession : IDisposable
     private RigctldRadio? radio;
     private ClusterClient? cluster;
     private StationNetwork? network;
+    private MessageSender? keyer;
 
     public AppSession(UserPaths paths, Settings settings)
     {
@@ -56,6 +58,8 @@ public sealed class AppSession : IDisposable
 
     public StationNetwork? Network => network;
 
+    public MessageSender? Keyer => keyer;
+
     public event EventHandler? Changed;
 
     public event EventHandler? ContestChanged;
@@ -151,6 +155,31 @@ public sealed class AppSession : IDisposable
         OpenContest(Logging.Instance.ContestNumber);
     }
 
+    /// Starts, restarts or stops the keyer, following what the settings say.
+    /// A keyer that will not open is reported; the program keeps running
+    /// without one.
+    public void ApplyKeyerSettings()
+    {
+        keyer?.Dispose();
+        keyer = null;
+        switch (Settings.KeyerKind.ToLowerInvariant())
+        {
+            case "cwdaemon":
+                keyer = new CwDaemonSender(Settings.KeyerHost, Settings.KeyerPort);
+                break;
+            case "winkeyer":
+                WinkeyerSender winkeyer = new(Settings.KeyerSerialPort);
+                winkeyer.Open();
+                keyer = winkeyer;
+                break;
+        }
+        if (keyer is not null)
+        {
+            _ = keyer.SetSpeedAsync(Settings.KeyerSpeed);
+        }
+        Changed?.Invoke(this, EventArgs.Empty);
+    }
+
     public void ConnectRadio()
     {
         radio?.Dispose();
@@ -204,6 +233,7 @@ public sealed class AppSession : IDisposable
         radio?.Dispose();
         cluster?.Dispose();
         network?.Dispose();
+        keyer?.Dispose();
         store?.Dispose();
     }