Read the rest of what a .udc file says, and score what N1MM scores

Two pieces of work on the scoring engine.

The .udc reader now takes N1MM's published scoring vocabulary: the full
PointsPerContact condition set, the PointsMultBy family, PowerMult, BonusPoints,
the multiplier sources and the settings that say which stations bring a
multiplier in. MultMult is a weight rather than a switch, as in N1MM's
ComputeScore. The entry categories and the sent exchange reach the rules in a
new ContestEntry, so a contest can score by the power category it is entered in
or by what this station sends.

Then every contest in a real N1MM log was scored again from these rules and
compared with the points and multiplier flags N1MM wrote. That found five bugs:
ARRL DX and IARU read the exchange from the wrong column, a stored " " was read
as a value rather than as empty, CQ WW RTTY's own Canadian area names were not
counted, a maritime mobile scored nothing, and a contact in a mode the contest
does not run scored as if it were in the contest.

docs/n1mm-interop.md has the check and what still differs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RoGtneMQaz4M9w7Kk49AVD

src/Nonemm.Core/ContestEntry.cs

@@ -0,0 +1,34 @@
+namespace Nonemm.Core;
+
+/// The entry the operator declared: the categories the sponsor's header asks
+/// for, and the exchange this station sends. Contests score by these — a QRP
+/// entry can be worth a multiple of what the same contacts score at high
+/// power, and a contest can pay by what the station itself sends.
+///
+/// The values are the Cabrillo category names, which is what the log file
+/// stores and what N1MM compares against.
+public sealed record ContestEntry
+{
+    public string OperatorCategory { get; init; } = "SINGLE-OP";
+
+    public string BandCategory { get; init; } = "ALL";
+
+    public string PowerCategory { get; init; } = "HIGH";
+
+    public string ModeCategory { get; init; } = "";
+
+    public string OverlayCategory { get; init; } = "";
+
+    public string StationCategory { get; init; } = "";
+
+    public string AssistedCategory { get; init; } = "NON-ASSISTED";
+
+    public string TransmitterCategory { get; init; } = "ONE";
+
+    public string TimeCategory { get; init; } = "";
+
+    /// What this station sends, as the operator typed it into the contest
+    /// setup. Empty until a contest is open, and then whatever N1MM would put
+    /// in the sent exchange box.
+    public string SentExchange { get; init; } = "";
+}