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)

tests/integration/chat-sse-broadcast.test.ts

@@ -0,0 +1,92 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { createMigratedTestDb } from '@/tests/helpers/db';
+import type { SqliteDatabase } from '@/lib/db/sqlite';
+import { UserRepository } from '@/repositories/UserRepository';
+import { ProjectRepository } from '@/repositories/ProjectRepository';
+import { ProjectMemberRepository } from '@/repositories/ProjectMemberRepository';
+import { ChatRepository } from '@/repositories/ChatRepository';
+import { NotificationRepository } from '@/repositories/NotificationRepository';
+import { NotificationService } from '@/services/NotificationService';
+import { ChatService } from '@/services/ChatService';
+import { SseHub, type SseClient } from '@/lib/sse/hub';
+
+describe('chat → SSE broadcast (integration)', () => {
+  let db: SqliteDatabase;
+  let service: ChatService;
+  let hub: SseHub;
+  let projectId: number;
+  let authorId: number;
+
+  beforeEach(() => {
+    db = createMigratedTestDb();
+    hub = new SseHub();
+    const users = new UserRepository(db);
+    authorId = users.create({
+      name: 'A',
+      email: 'a@example.com',
+      passwordHash: 'h',
+    }).id;
+    projectId = new ProjectRepository(db).create({
+      name: 'P',
+      ownerId: authorId,
+    }).id;
+    const members = new ProjectMemberRepository(db);
+    members.add(projectId, authorId, 'admin');
+    service = new ChatService(
+      new ChatRepository(db),
+      members,
+      users,
+      new NotificationService(new NotificationRepository(db)),
+      hub
+    );
+  });
+
+  afterEach(() => db.close());
+
+  function subscribe(projectId: number): SseClient & { received: string[] } {
+    const received: string[] = [];
+    const client: SseClient & { received: string[] } = {
+      received,
+      enqueue: (c) => received.push(c),
+      close: () => undefined,
+    };
+    hub.addClient(projectId, client);
+    return client;
+  }
+
+  it('a subscribed client receives the created message event in SSE format', () => {
+    const client = subscribe(projectId);
+
+    const message = service.sendMessage(authorId, projectId, 'hello realtime');
+
+    expect(client.received).toHaveLength(1);
+    const raw = client.received[0];
+    expect(raw).toMatch(/^data: .+\n\n$/);
+    const parsed = JSON.parse(raw.replace(/^data: /, '').replace(/\n\n$/, ''));
+    expect(parsed.type).toBe('chat.message.created');
+    expect(parsed.data.message.id).toBe(message.id);
+    expect(parsed.data.message.body).toBe('hello realtime');
+  });
+
+  it('a client in another project does not receive the message', () => {
+    const otherClient = subscribe(99999);
+
+    service.sendMessage(authorId, projectId, 'hello');
+
+    expect(otherClient.received).toHaveLength(0);
+  });
+
+  it('delete broadcasts a deleted event with the message id', () => {
+    const client = subscribe(projectId);
+    const message = service.sendMessage(authorId, projectId, 'to be deleted');
+    client.received.length = 0;
+
+    service.deleteMessage(authorId, message.id);
+
+    const parsed = JSON.parse(
+      client.received[0].replace(/^data: /, '').replace(/\n\n$/, '')
+    );
+    expect(parsed.type).toBe('chat.message.deleted');
+    expect(parsed.data.id).toBe(message.id);
+  });
+});