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/GameLogic/CastleSiege/CastleSiegeConfiguration.cs

@@ -35,6 +35,12 @@ public class CastleSiegeConfiguration
     /// <summary>Gets or sets how long the war (siege) period lasts.</summary>
     public TimeSpan SiegeDuration { get; set; } = TimeSpan.FromMinutes(10);
 
+    /// <summary>
+    /// Gets or sets how long the guild master must hold the Crown (with both switches held and all gates down)
+    /// to capture the throne. The client shows a 60-second countdown, so 60s matches the on-screen timer.
+    /// </summary>
+    public TimeSpan CrownHoldDuration { get; set; } = TimeSpan.FromSeconds(60);
+
     /// <summary>
     /// Gets or sets the registration fee (in zen) a guild master must pay to register the guild
     /// for the siege. 0 disables the fee.