feat(guild_chat): messages window + system events

- GuildChatService.EmitSystemEventAsync: replaces no-op stub with real
  chat-row insertion via _msgs.AppendAsync (per-guild monotonic id).
- GuildChatService.GetWindowAsync: real implementation — verifies caller
  membership, delegates to IGuildChatMessageRepository.GetWindowAsync
  (direction 1=OLD/2=NEW/3=BOTH, limit 50), returns adaptive wait interval
  (ChatPollActiveSeconds when messages returned, ChatPollIdleSeconds otherwise).
- Drop unused repo injections from GuildChatService (guilds, invites, joinRequests).
- GuildChatController.Messages: wires the full response — chat_message[],
  users[] (deduplicated author profiles with Emblem+Degree nav includes),
  maintenance_card_list (empty until maintenance service lands), wait_interval.
- GuildChatPollTests (7 integration tests): fresh-guild CreateGuild event,
  sequenced Create+Join ordering, direction=NEW filter, direction=BOTH window,
  users[] deduplication, empty result for viewer-not-in-guild, active vs idle
  interval comparison. All 7 pass; full suite 1515/1515.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.Database/Services/Guild/GuildChatService.cs

@@ -1,3 +1,5 @@
+using SVSim.Database.Entities.Guild;
+using SVSim.Database.Models.Config;
 using SVSim.Database.Repositories.Guild;
 using SVSim.Database.Services;
 
@@ -5,31 +7,65 @@ namespace SVSim.Database.Services.Guild;
 
 public sealed class GuildChatService : IGuildChatService
 {
-    private readonly IGuildRepository _guilds;
     private readonly IGuildMemberRepository _members;
-    private readonly IGuildInviteRepository _invites;
-    private readonly IGuildJoinRequestRepository _joinRequests;
-    private readonly IGuildChatMessageRepository _chatMessages;
-    private readonly IGameConfigService _config;
+    private readonly IGuildChatMessageRepository _msgs;
+    private readonly IGameConfigService _cfg;
 
     public GuildChatService(
-        IGuildRepository guilds,
         IGuildMemberRepository members,
-        IGuildInviteRepository invites,
-        IGuildJoinRequestRepository joinRequests,
-        IGuildChatMessageRepository chatMessages,
-        IGameConfigService config)
+        IGuildChatMessageRepository msgs,
+        IGameConfigService cfg)
     {
-        _guilds = guilds;
         _members = members;
-        _invites = invites;
-        _joinRequests = joinRequests;
-        _chatMessages = chatMessages;
-        _config = config;
+        _msgs    = msgs;
+        _cfg     = cfg;
     }
 
-    public Task<ChatWindow> GetWindowAsync(long viewerId, int startMessageId, int direction, int waitIntervalHint, CancellationToken ct = default)
-        => throw new NotImplementedException();
+    // ── System-event emission ────────────────────────────────────────────────
+
+    public async Task EmitSystemEventAsync(
+        int guildId,
+        long actorViewerId,
+        GuildChatMessageType type,
+        string? body = null,
+        CancellationToken ct = default)
+    {
+        var msg = new GuildChatMessage
+        {
+            GuildId         = guildId,
+            AuthorViewerId  = actorViewerId,
+            MessageType     = type,
+            Body            = body ?? "",
+            CreatedAt       = DateTime.UtcNow,
+        };
+        await _msgs.AppendAsync(msg, ct);
+    }
+
+    // ── Window query ─────────────────────────────────────────────────────────
+
+    public async Task<ChatWindow> GetWindowAsync(
+        long viewerId,
+        int startMessageId,
+        int direction,
+        int waitIntervalHint,
+        CancellationToken ct = default)
+    {
+        var membership = await _members.GetMembershipAsync(viewerId, ct);
+        if (membership is null)
+        {
+            var idleInterval = _cfg.Get<GuildConfig>().ChatPollIdleSeconds;
+            return new(Array.Empty<GuildChatMessage>(), idleInterval);
+        }
+
+        const int limit = 50;
+        var msgs = await _msgs.GetWindowAsync(membership.GuildId, startMessageId, direction, limit, ct);
+
+        var cfg = _cfg.Get<GuildConfig>();
+        int wait = msgs.Count == 0 ? cfg.ChatPollIdleSeconds : cfg.ChatPollActiveSeconds;
+        return new(msgs, wait);
+    }
+
+    // ── Not-yet-implemented stubs ────────────────────────────────────────────
 
     public Task<ChatPostResult> PostTextOrStampAsync(long viewerId, int type, string message, CancellationToken ct = default)
         => throw new NotImplementedException();
@@ -48,8 +84,4 @@ public sealed class GuildChatService : IGuildChatService
 
     public Task<string?> GetDeckLogAsync(long viewerId, int messageId, CancellationToken ct = default)
         => throw new NotImplementedException();
-
-    // No-op skeleton — will be wired in Phase 5.
-    public Task EmitSystemEventAsync(int guildId, long actorViewerId, Entities.Guild.GuildChatMessageType type, string? body = null, CancellationToken ct = default)
-        => Task.CompletedTask;
 }