feat(m8): SSE hub + realtime chat with mentions, tests, e2e

- SseHub (project-scoped client mgmt + broadcast, implements SseBroadcaster)
  with SSE-formatted payload; singleton getSseHub
- ChatRepository (message CRUD, soft-delete, search, pagination, project
  isolation) + ChatService (membership permission, send/edit/delete,
  @email mention -> mention notification, SSE broadcast of created/updated/deleted)
- SSE stream endpoint (ReadableStream + heartbeat + abort cleanup, membership)
- Chat message API routes (history/send/edit/delete)
- ChatWindow client (EventSource auto-reconnect, history fetch, realtime
  append/update/delete), chat page, ProjectNav チャット link
- SseEvent type now carries ChatMessage for chat events
- Unit (SseHub, ChatRepository, ChatService) + integration chat-sse-broadcast
  + e2e chat-sse (two contexts realtime)

lib/api/services.ts

@@ -11,6 +11,9 @@ import { BoardService } from '@/services/BoardService';
 import { BoardRepository } from '@/repositories/BoardRepository';
 import { NoteService } from '@/services/NoteService';
 import { ProjectNoteRepository } from '@/repositories/ProjectNoteRepository';
+import { ChatService } from '@/services/ChatService';
+import { ChatRepository } from '@/repositories/ChatRepository';
+import { getSseHub } from '@/lib/sse/hub';
 
 /**
  * Route Handler用に各Repository/Serviceを構築するファクトリ。
@@ -54,6 +57,17 @@ export function createNoteService(): NoteService {
   );
 }
 
+export function createChatService(): ChatService {
+  const db = getDb();
+  return new ChatService(
+    new ChatRepository(db),
+    new ProjectMemberRepository(db),
+    new UserRepository(db),
+    new NotificationService(new NotificationRepository(db)),
+    getSseHub()
+  );
+}
+
 export function createUserRepository(): UserRepository {
   return new UserRepository(getDb());
 }

lib/sse/hub.ts

@@ -0,0 +1,65 @@
+import type { SseBroadcaster, SseEvent } from '@/lib/types';
+
+/**
+ * SSEクライアントの抽象。ReadableStreamのcontrollerを包む。
+ */
+export interface SseClient {
+  enqueue(chunk: string): void;
+  close(): void;
+}
+
+/**
+ * プロジェクト単位のSSEクライアント管理・イベント配信を行うHub。
+ * 配信は当該プロジェクトのクライアントのみに行い、他プロジェクトへ漏らさない。
+ * モジュールシングルトン(getSseHub)でプロセス内共有する。
+ */
+export class SseHub implements SseBroadcaster {
+  private readonly clients = new Map<number, Set<SseClient>>();
+
+  addClient(projectId: number, client: SseClient): void {
+    let set = this.clients.get(projectId);
+    if (!set) {
+      set = new Set();
+      this.clients.set(projectId, set);
+    }
+    set.add(client);
+  }
+
+  removeClient(projectId: number, client: SseClient): void {
+    this.clients.get(projectId)?.delete(client);
+  }
+
+  broadcast(projectId: number, event: SseEvent): void {
+    const set = this.clients.get(projectId);
+    if (!set || set.size === 0) return;
+    const payload = `data: ${JSON.stringify(event)}\n\n`;
+    for (const client of set) {
+      try {
+        client.enqueue(payload);
+      } catch {
+        // 書き込み失敗(切断済み等)のクライアントは除去
+        set.delete(client);
+      }
+    }
+  }
+
+  /** テスト/監視用: プロジェクトの接続クライアント数 */
+  getClientCount(projectId: number): number {
+    return this.clients.get(projectId)?.size ?? 0;
+  }
+}
+
+let hubInstance: SseHub | null = null;
+
+/** プロセス全体で共有するSseHubシングルトンを取得する */
+export function getSseHub(): SseHub {
+  if (!hubInstance) {
+    hubInstance = new SseHub();
+  }
+  return hubInstance;
+}
+
+/** テスト用途: シングルトンをリセットする */
+export function resetSseHub(): void {
+  hubInstance = null;
+}

lib/types/index.ts

@@ -277,16 +277,25 @@ export type NotificationEvent =
       projectMemberIds: number[];
     });
 
-/** SSE配信イベント(M8でSseHubが扱う)。M5ではbroadcasterの型として使用 */
+/** SSE配信イベント(M8でSseHubが扱う)。 */
 export type SseEvent =
-  | { type: 'notification.created'; data: { projectId: number | null } }
-  | { type: 'chat.message.created'; data: { projectId: number } }
-  | { type: 'chat.message.updated'; data: { projectId: number } }
-  | { type: 'chat.message.deleted'; data: { projectId: number; id: number } }
+  | {
+      type: 'chat.message.created';
+      data: { projectId: number; message: ChatMessage };
+    }
+  | {
+      type: 'chat.message.updated';
+      data: { projectId: number; message: ChatMessage };
+    }
+  | {
+      type: 'chat.message.deleted';
+      data: { projectId: number; id: number };
+    }
   | { type: 'todo.updated'; data: { projectId: number } }
   | { type: 'file.uploaded'; data: { projectId: number } }
   | { type: 'meeting.created'; data: { projectId: number } }
-  | { type: 'note.updated'; data: { projectId: number } };
+  | { type: 'note.updated'; data: { projectId: number } }
+  | { type: 'notification.created'; data: { projectId: number | null } };
 
 /** SSE配信を行うコンポーネントの抽象(M8のSseHubが実装) */
 export interface SseBroadcaster {