Implement Guild Alliance System

[Copilot]

Implements the foundational guild alliance and hostility system required as a prerequisite for Castle Siege. Multiple guilds can form an alliance under a master guild, with full CRUD lifecycle and transitive hostility support.

Core Server Logic

• IGuildServer — Added 8 new methods: CreateAllianceAsync, RemoveAllianceGuildAsync, DisbandAllianceAsync, GetAllianceGuildsAsync, IsAllianceMasterAsync, GetAllianceMasterIdAsync, SetHostilityAsync, GetGuildRelationshipAsync. Added AllianceGuildEntry and GuildRelationship types.
• GuildServer — Full implementation. Alliance master is identified by self-referencing AllianceGuild property. Max alliance size enforced via MaxAllianceSize = 5 constant. Transitive hostility: if any guild in Alliance A is hostile to any guild in Alliance B, all members across both alliances are considered rivals.
• GuildPosition — Added AssistantMaster value for castle siege NPC management.

Publisher & Context

• IGuildChangePublisher — Added AllianceCreatedAsync, AllianceGuildRemovedAsync, AllianceDisbandedAsync.
• GameServerContext.ForEachAlliancePlayerAsync — Removed the TODO stub; now queries GuildServer.GetAllianceGuildsAsync to iterate online players across all guilds in the alliance.

Network Packets (Server→Client)

Three new server-to-client packets added to XML, generated structs, ref structs, and ConnectionExtensions:

Code	Name	Purpose
0xE5	GuildRelationshipRequest	Forward alliance/hostility request to target guild master
0xE6	GuildRelationshipChangeResult	Result of relationship change back to requester
0xE9	AllianceList	List of guilds in the alliance

Game Logic & Handlers

• GuildRelationshipChangeAction — Validates guild master status, routes join/leave/hostility requests. Alliance join uses a PendingAllianceRequest property on Player for the two-step request/response flow (mirroring the guild war pattern).
• Packet handlers — GuildRelationshipChangeHandlerPlugIn (C1 E5), GuildRelationshipChangeResponseHandlerPlugIn (C1 E6), AllianceListRequestHandlerPlugIn (C1 E9), AllianceGroupHandlerPlugIn + RemoveAllianceGuildHandlerPlugIn (C1 EB 01).
• Remote view plugins — ShowGuildRelationshipRequestPlugIn, ShowGuildRelationshipChangeResultPlugIn, ShowAllianceListPlugIn.

Dapr

Both GuildChangePublisher and ServerClients/GuildServer updated to implement the new interface methods.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Guild Alliance System</issue_title>
<issue_description>## Summary

Implement the Guild Alliance system, which allows multiple guilds to form an alliance under an alliance master guild. This is a prerequisite for Castle Siege, where entire alliances participate as a unit. The system also includes guild hostility (rival relationships).

Prerequisites

None — this is the foundational phase.

Background

OpenMU already has partial support for alliances:

• Interfaces.Guild has AllianceGuild and Hostility navigation properties.
• DataModel.Entities.Guild extends Interfaces.Guild with Members.
• Alliance chat routes through IEventPublisher.AllianceMessageAsync.
• IGameServerContext.ForEachAlliancePlayerAsync is declared but needs implementation.
• Client→Server packet docs exist: C1-E6-GuildRelationshipChangeResponse, C1-E9-RequestAllianceList, C1-EB-01-RemoveAllianceGuildRequest.

What's missing is the actual server-side CRUD logic for alliances and the corresponding message handlers.

Requirements

1. IGuildServer Extensions (Interfaces/IGuildServer.cs)

Add these methods to the IGuildServer interface:

ValueTask<bool> CreateAllianceAsync(uint masterGuildId, uint targetGuildId);
ValueTask<bool> RemoveAllianceGuildAsync(uint masterGuildId, uint targetGuildId);
ValueTask<bool> DisbandAllianceAsync(uint masterGuildId);
ValueTask<IImmutableList<AllianceGuildEntry>> GetAllianceGuildsAsync(uint guildId);
ValueTask<bool> IsAllianceMasterAsync(uint guildId);
ValueTask<uint> GetAllianceMasterIdAsync(uint guildId);
ValueTask<bool> SetHostilityAsync(uint guildId, uint targetGuildId, bool create);
ValueTask<GuildRelationship> GetGuildRelationshipAsync(uint guild1, uint guild2);

Add supporting types:

public class AllianceGuildEntry
{
    public string GuildName { get; set; }
    public uint GuildId { get; set; }
}

public enum GuildRelationship : byte
{
    None = 0,
    Union = 1,
    Rival = 2,
}

2. GuildPosition Extension (Interfaces/GuildPosition.cs)

Add AssistantMaster value (needed for castle siege NPC management):

public enum GuildPosition : byte
{
    Undefined,
    NormalMember,
    GuildMaster,
    BattleMaster,
    AssistantMaster, // NEW
}

3. GuildServer Implementation (GuildServer/GuildServer.cs)

Implement the alliance CRUD methods:

• CreateAllianceAsync: Set AllianceGuild on both guilds. The requesting guild becomes the alliance master (self-referencing AllianceGuild). The target guild's AllianceGuild is set to the master. Enforce configurable max alliance size (default 5). Both guild masters must agree (request/response flow similar to guild join).
• RemoveAllianceGuildAsync: Only the alliance master can remove member guilds. Clear the removed guild's AllianceGuild.
• DisbandAllianceAsync: Clear AllianceGuild on all member guilds.
• GetAllianceGuildsAsync: Find all guilds in the _guildDictionary whose Guild.AllianceGuild matches the given guild's alliance master. Also query the database for offline alliance members.
• IsAllianceMasterAsync: A guild is the alliance master when guild.AllianceGuild points to itself.
• GetAllianceMasterIdAsync: Return the runtime uint ID of the alliance master guild.
• SetHostilityAsync: Set or clear Guild.Hostility on the requesting guild.
• GetGuildRelationshipAsync: Return Union if both guilds share the same AllianceGuild, Rival if hostility exists (transitively through alliances), None otherwise.

Hostility transitivity rule: If any guild in Alliance A has Hostility pointing to any guild in Alliance B, all members of both alliances are rivals.

4. IGuildChangePublisher Extensions (GuildServer/IGuildChangePublisher.cs)

Add methods to broadcast alliance changes to game servers:

ValueTask AllianceCreatedAsync(uint masterGuildId, uint memberGuildId);
ValueTask AllianceGuildRemovedAsync(uint masterGuildId, uint memberGuildId);
ValueTask AllianceDisbandedAsync(uint masterGuildId);

Implement in GuildChangeToGameServerPublisher.cs.

5. Player Action (GameLogic/PlayerActions/Guild/GuildRelationshipChangeAction.cs) — New file

Validates the request:

• Player must be a guild master.
• For alliance creation: target guild must exist, not already in an alliance, max size not exceeded.
• For alliance removal: player must be the alliance master.
• For hostility: target guild must exist.

Calls the appropriate IGuildServer method via IGameServerContext.GuildServer.

6. Message Handlers — New files in GameServer/MessageHandler/Guild/

Follow the pattern of existing handlers (e.g., GuildRequestHandlerPlugIn.cs):

• GuildRelationshipChangeHandlerPlugIn: Handles C1-E5 (or the correct headcode for guild relationship requests). Parses the packet, calls `GuildRelationshipC...

• Fixes Guild Alliance System #720

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