feat(CS): authentic Crown-hold throne capture (S6 protocol) replacing Sinior-talk

Break all gates + hold both switches (defenses down) -> the Crown shield drops
(C1 B2 16=0). The guild master then stands on the Crown (176,212) and holds for
CrownHoldDuration (default 60s, client shows a 60s countdown via C1 B2 15) to
capture; capture broadcasts C1 B2 18 + golden text and sets the occupier. Losing a
switch or leaving the crown resets the hold (contestable until the siege timer ends).
Sinior (223) is now informational guidance. +2 tests (14 total).

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

src/GameServer/RemoteView/CastleSiege/CastleSiegeStatusViewPlugIn.cs

@@ -101,4 +101,82 @@ public class CastleSiegeStatusViewPlugIn : ICastleSiegeStatusViewPlugIn
 
         await connection.SendAsync(WritePacket).ConfigureAwait(false);
     }
+
+    /// <inheritdoc />
+    public async ValueTask SetCrownShieldAsync(bool down)
+    {
+        var connection = this._player.Connection;
+        if (connection is null)
+        {
+            return;
+        }
+
+        int WritePacket()
+        {
+            // C1 0C B2 16 <state> <pad> <dword=0> ; state 0 = shield down, 1 = shield up
+            var span = connection.Output.GetSpan(12)[..12];
+            span.Clear();
+            span[0] = 0xC1;
+            span[1] = 0x0C;
+            span[2] = 0xB2;
+            span[3] = 0x16;
+            span[4] = (byte)(down ? 0 : 1);
+            return span.Length;
+        }
+
+        await connection.SendAsync(WritePacket).ConfigureAwait(false);
+    }
+
+    /// <inheritdoc />
+    public async ValueTask SetCrownRegistAsync(byte state, uint accessMilliseconds)
+    {
+        var connection = this._player.Connection;
+        if (connection is null)
+        {
+            return;
+        }
+
+        int WritePacket()
+        {
+            // C1 0C B2 15 <state> <pad3> <accessMs:4 LE @offset 8>
+            var span = connection.Output.GetSpan(12)[..12];
+            span.Clear();
+            span[0] = 0xC1;
+            span[1] = 0x0C;
+            span[2] = 0xB2;
+            span[3] = 0x15;
+            span[4] = state;
+            System.Buffers.Binary.BinaryPrimitives.WriteUInt32LittleEndian(span.Slice(8, 4), accessMilliseconds);
+            return span.Length;
+        }
+
+        await connection.SendAsync(WritePacket).ConfigureAwait(false);
+    }
+
+    /// <inheritdoc />
+    public async ValueTask AnnounceSealCapturedAsync(string guildName)
+    {
+        var connection = this._player.Connection;
+        if (connection is null)
+        {
+            return;
+        }
+
+        int WritePacket()
+        {
+            // C1 0D B2 18 <state=1> <guildName[8] utf8>
+            var span = connection.Output.GetSpan(13)[..13];
+            span.Clear();
+            span[0] = 0xC1;
+            span[1] = 0x0D;
+            span[2] = 0xB2;
+            span[3] = 0x18;
+            span[4] = 1;
+            var bytes = System.Text.Encoding.UTF8.GetBytes(guildName);
+            bytes.AsSpan(0, Math.Min(8, bytes.Length)).CopyTo(span.Slice(5, 8));
+            return span.Length;
+        }
+
+        await connection.SendAsync(WritePacket).ConfigureAwait(false);
+    }
 }