BattleTech egg builder, catalog, and golden-egg DiffTests (BT port phases 1-2)

New TeslaConsole.BattleTech namespace mirroring TeslaConsole.RedPlanet's
mission layer: BTMission/BTFreeForAllMission (egg serializer; RP wire framing
and ordinal bitmaps reused verbatim), BTParticipant/BTPlayer/BTCamera (BT
participant fields: advancedDamage, experience, vehicleValue, patch, role),
and the BTConfig/BTScenario/BTMap/BTVehicle/BTWeather/BTRole catalog loaded
from BattleTech\BTConfig.xml (reconstructed from the Mac Console 4.10 ini BT
tree). Free For All and No Return share one mission class - both send
scenario=freeforall; the mode is the role assigned to each pilot.

BTGoldenEggTests (7 tests, recovered-only) diff the generated egg
field-by-field against two eggs captured from the original consoles
(cavern.egg, TESTARN.EGG): order-independent per-section compare with
font-rendered bitmap pixel rows excluded, ordinal art byte-exact vs
TESTARN.EGG, EggFileMessage framing reassembly, role de-dup, No Return role
semantics, and shipped-catalog contents. Invoker gains BTEggString/
BTEggFraming reflection cases.

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

Console/TeslaConsole.BattleTech/BTMap.cs

@@ -0,0 +1,44 @@
+using System.Drawing;
+using System.IO;
+using System.Windows.Forms;
+using System.Xml;
+
+namespace TeslaConsole.BattleTech;
+
+public class BTMap
+{
+	private readonly string mKey;
+
+	private readonly string mName;
+
+	private readonly string mImagePath;
+
+	public string Key => mKey;
+
+	public string Name => mName;
+
+	public Image Image
+	{
+		get
+		{
+			if (mImagePath == null)
+			{
+				return null;
+			}
+			return ImageCache.GetImage(Path.Combine(Path.GetDirectoryName(Application.ExecutablePath), mImagePath));
+		}
+	}
+
+	internal BTMap(XmlNode mapNode)
+	{
+		XmlAttribute xmlAttribute = mapNode.Attributes["image"];
+		mKey = mapNode.Attributes["key"].InnerText;
+		mName = mapNode.Attributes["name"].InnerText;
+		mImagePath = xmlAttribute?.InnerText;
+	}
+
+	public override string ToString()
+	{
+		return mName;
+	}
+}