feat(CS): on-map siege countdown timer (S6 client protocol C1 B2 17/1E)

Client already renders the siege-map countdown but never received the packets.
New ICastleSiegeStatusViewPlugIn + RemoteView impl send the raw S6 packets:
C1 B2 17 (battle start/stop flag, arms the countdown) and C1 B2 1E (remaining
hour/minute). CastleSiegeEventPlugIn broadcasts them to players on the battle map
every 10s during Siege and sends stop at Settlement. No client changes. +1 test.

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

src/GameServer/RemoteView/CastleSiege/CastleSiegeStatusViewPlugIn.cs

@@ -0,0 +1,78 @@
+// <copyright file="CastleSiegeStatusViewPlugIn.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.GameServer.RemoteView.CastleSiege;
+
+using System.Runtime.InteropServices;
+using MUnique.OpenMU.GameLogic.Views.CastleSiege;
+using MUnique.OpenMU.Network;
+using MUnique.OpenMU.PlugIns;
+
+/// <summary>
+/// The default implementation of <see cref="ICastleSiegeStatusViewPlugIn"/> which sends the Season 6
+/// Castle Siege countdown packets straight to the game client as raw bytes (no packet-struct exists yet).
+/// </summary>
+[PlugIn]
+[Display(Name = "Castle Siege Status View", Description = "Sends the Castle Siege on-map countdown/state packets (C1 B2 17 / C1 B2 1E).")]
+[Guid("CA5710A0-7A1B-4C2D-8E3F-0000000017E0")]
+public class CastleSiegeStatusViewPlugIn : ICastleSiegeStatusViewPlugIn
+{
+    private readonly RemotePlayer _player;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CastleSiegeStatusViewPlugIn"/> class.
+    /// </summary>
+    /// <param name="player">The player.</param>
+    public CastleSiegeStatusViewPlugIn(RemotePlayer player) => this._player = player;
+
+    /// <inheritdoc />
+    public async ValueTask SetBattleStateAsync(bool started)
+    {
+        var connection = this._player.Connection;
+        if (connection is null)
+        {
+            return;
+        }
+
+        int WritePacket()
+        {
+            // C1 09 B2 17 <started> <crownAccessTime:4 bytes = 0>
+            var span = connection.Output.GetSpan(9)[..9];
+            span.Clear();
+            span[0] = 0xC1;
+            span[1] = 0x09;
+            span[2] = 0xB2;
+            span[3] = 0x17;
+            span[4] = (byte)(started ? 1 : 0);
+            return span.Length;
+        }
+
+        await connection.SendAsync(WritePacket).ConfigureAwait(false);
+    }
+
+    /// <inheritdoc />
+    public async ValueTask SetTimerAsync(byte hour, byte minute)
+    {
+        var connection = this._player.Connection;
+        if (connection is null)
+        {
+            return;
+        }
+
+        int WritePacket()
+        {
+            // C1 06 B2 1E <hour> <minute>
+            var span = connection.Output.GetSpan(6)[..6];
+            span[0] = 0xC1;
+            span[1] = 0x06;
+            span[2] = 0xB2;
+            span[3] = 0x1E;
+            span[4] = hour;
+            span[5] = minute;
+            return span.Length;
+        }
+
+        await connection.SendAsync(WritePacket).ConfigureAwait(false);
+    }
+}