perf: Migrate Old Guild System gumps to DynamicGump (#2420)

## Summary

Migrates the Old Guild System (pre-AOS guild stones) gumps from the legacy `Gump` class to `DynamicGump`, following the same pattern used for the Quest gump migration in #2416. All concrete gumps now have private constructors gated by static `DisplayTo` entry points (empty-gump rule), and `Singleton => true` is set across the board so reopening a sibling dialog automatically closes the previous one.

**Migrated gumps:**
- `GuildGump` - main guild dialog
- `GuildmasterGump` - guildmaster functions
- `GuildCharterGump` - charter and website display
- `GuildWarGump` - warfare status (kept as player-facing)
- `GuildWarAdminGump` - war menu (retained as player-facing - reachable from `GuildmasterGump`'s WAR button by guildmasters)
- `GuildChangeTypeGump` - Standard/Order/Chaos selection

**Abstract bases:** `GuildListGump` and `GuildMobileListGump` keep their shared list-rendering chrome inside a single concrete `BuildLayout` on the abstract class and expose a `protected abstract void BuildHeader(ref DynamicGumpBuilder builder)` hook for subclasses (replacing the old `Design()` override). This mirrors the abstract-base treatment used for the ML quest base in the quest-gump migration PR.

**Concrete subclasses migrated alongside the abstract bases:**
- `GuildListGump` subclasses: `GuildAcceptWarGump`, `GuildDeclarePeaceGump`, `GuildDeclareWarGump`, `GuildRejectWarGump`, `GuildRescindDeclarationGump`
- `GuildMobileListGump` subclasses: `DeclareFealtyGump`, `GrantGuildTitleGump`, `GuildAdminCandidatesGump`, `GuildCandidatesGump`, `GuildDismissGump`, `GuildRosterGump`

**Cliloc rule:** Every gump bakes per-instance dynamic content (guild names, member names, war declarations, candidate lists), which would defeat `StaticGump<T>` caching. Per the cliloc rule, all are `DynamicGump`.

**External callers updated:** the prompt files (`GuildAbbrvPrompt`, `GuildCharterPrompt`, `GuildDeclareWarPrompt`, `GuildNamePrompt`, `GuildTitlePrompt`, `GuildWebsitePrompt`), `RecruitTarget`, the `Guildstone` item, and the New Guild System `GuildInfoGump`'s Order/Chaos handler all now go through static `DisplayTo` entry points instead of `new XGump(...)`.

Projects/Server/Guild.cs

@@ -62,7 +62,7 @@ public abstract class BaseGuild : ISerializable
 
     public abstract void OnDelete(Mobile mob);
 
-    public static BaseGuild FindByName(string name)
+    public static BaseGuild FindByName(ReadOnlySpan<char> name)
     {
         foreach (var g in World.Guilds.Values)
         {
@@ -75,7 +75,7 @@ public abstract class BaseGuild : ISerializable
         return null;
     }
 
-    public static BaseGuild FindByAbbrev(string abbr)
+    public static BaseGuild FindByAbbrev(ReadOnlySpan<char> abbr)
     {
         foreach (var g in World.Guilds.Values)
         {
@@ -88,19 +88,29 @@ public abstract class BaseGuild : ISerializable
         return null;
     }
 
-    public static HashSet<BaseGuild> Search(string find)
+    public static HashSet<BaseGuild> Search(ReadOnlySpan<char> find)
     {
-        var words = find.ToLower().Split(' ');
         var results = new HashSet<BaseGuild>();
+        find = find.Trim();
+        if (find.IsEmpty)
+        {
+            return results;
+        }
 
         foreach (var g in World.Guilds.Values)
         {
-            var name = g.Name;
+            var name = g.Name.AsSpan();
 
             var all = true;
-            foreach (var t in words)
+            foreach (var wordRange in find.Split(' '))
             {
-                if (name.InsensitiveIndexOf(t) == -1)
+                var word = find[wordRange];
+                if (word.IsEmpty)
+                {
+                    continue;
+                }
+
+                if (name.InsensitiveContains(word))
                 {
                     all = false;
                     break;