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>

tests/Nonemm.Session.Tests/MessageExpanderTests.cs

@@ -0,0 +1,54 @@
+using Nonemm.Contests;
+using Nonemm.Contests.Rules;
+using Nonemm.Core;
+using Nonemm.Storage;
+
+namespace Nonemm.Session.Tests;
+
+public class MessageExpanderTests
+{
+    private static LoggingSession Session()
+    {
+        FakeLogStore store = new();
+        ContestInstance instance = store.AddContest(new ContestInstance
+        {
+            ContestNumber = 0,
+            ContestName = "CQWW",
+            SentExchange = "14",
+        });
+        return new LoggingSession(
+            store,
+            new CqWorldWide(ModeCategory.Cw),
+            instance,
+            new StationInfo { Callsign = "DL1ABC", CqZone = 14, Name = "Erik" },
+            null);
+    }
+
+    [Fact]
+    public void MyCallAndTheirCallAreFilledIn()
+    {
+        LoggingSession session = Session();
+        session.Entry.Call = "JA1XYZ";
+        Assert.Equal("JA1XYZ DE DL1ABC", MessageExpander.Expand("{CALL} DE {MYCALL}", session));
+    }
+
+    [Fact]
+    public void TheSentExchangeComesFromTheContestSetup() =>
+        Assert.Equal("599 14", MessageExpander.Expand("{SENTRST} {EXCH}", Session()));
+
+    [Fact]
+    public void HashIsTheSerialNumber() =>
+        Assert.Equal("NR 1", MessageExpander.Expand("NR #", Session()));
+
+    [Fact]
+    public void CutNumbersReplaceZeroAndNine() =>
+        Assert.Equal("5NN", MessageExpander.Expand("{SENTRSTCUT}", Session()));
+
+    [Fact]
+    public void AMacroThatIsNotKnownDisappears() =>
+        Assert.Equal("TU ", MessageExpander.Expand("TU {NOTAMACRO}", Session()));
+
+    [Fact]
+    public void AnUnclosedMacroIsLeftAsTyped() =>
+        Assert.Equal("TU {MYCALL", MessageExpander.Expand("TU {MYCALL", Session()));
+}