feat(hs): add Heykel Savasi event map skeleton (map 90)

Adds HeykelSavasiMap (BaseMapInitializer, Number=90/World91) as an empty
terrain-only skeleton and registers it in GameMapsInitializer. Statue/guard
monster definitions and spawns are added by later Heykel Savasi tasks.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/Persistence/Initialization/VersionSeasonSix/GameMapsInitializer.cs

@@ -105,6 +105,7 @@ public class GameMapsInitializer : GameMapsInitializerBase
             yield return typeof(Debenter);
             yield return typeof(Uruk);
             yield return typeof(Ferea);
+            yield return typeof(HeykelSavasiMap);
         }
     }
 }

src/Persistence/Initialization/VersionSeasonSix/Maps/HeykelSavasiMap.cs

@@ -0,0 +1,66 @@
+// <copyright file="HeykelSavasiMap.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence.Initialization.VersionSeasonSix.Maps;
+
+/// <summary>
+/// The initialization for the Heykel Savasi event map.
+/// Statue/guard monster definitions and NPC/monster spawns are added by later
+/// Heykel Savasi tasks; for now this is an empty terrain-only skeleton.
+/// </summary>
+/// <remarks>
+/// The MU client loads world folder <c>World{Number + 1}</c>, so server map
+/// Number 90 corresponds to client World91.
+/// </remarks>
+internal class HeykelSavasiMap : BaseMapInitializer
+{
+    /// <summary>
+    /// The Number of the Map.
+    /// </summary>
+    internal const byte Number = 90;
+
+    /// <summary>
+    /// The Name of the Map.
+    /// </summary>
+    internal const string Name = "Heykel Savasi";
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="HeykelSavasiMap"/> class.
+    /// </summary>
+    /// <param name="context">The context.</param>
+    /// <param name="gameConfiguration">The game configuration.</param>
+    public HeykelSavasiMap(IContext context, GameConfiguration gameConfiguration)
+        : base(context, gameConfiguration)
+    {
+    }
+
+    /// <inheritdoc/>
+    protected override byte MapNumber => Number;
+
+    /// <inheritdoc/>
+    protected override string MapName => Name;
+
+    /// <inheritdoc/>
+    protected override byte SafezoneMapNumber => Lorencia.Number;
+
+    /// <inheritdoc/>
+    protected override IEnumerable<MonsterSpawnArea> CreateNpcSpawns()
+    {
+        // Event NPCs are added by later Heykel Savasi tasks.
+        yield break;
+    }
+
+    /// <inheritdoc/>
+    protected override IEnumerable<MonsterSpawnArea> CreateMonsterSpawns()
+    {
+        // Statue/guard monster spawns are added by later Heykel Savasi tasks.
+        yield break;
+    }
+
+    /// <inheritdoc/>
+    protected override void CreateMonsters()
+    {
+        // Statue/guard MonsterDefinitions are added by later Heykel Savasi tasks.
+    }
+}