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/unit/repositories/ChatRepository.test.ts

@@ -0,0 +1,85 @@
+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';
+
+describe('ChatRepository', () => {
+  let db: SqliteDatabase;
+  let repo: ChatRepository;
+  let projectId: number;
+  let authorId: number;
+
+  beforeEach(() => {
+    db = createMigratedTestDb();
+    repo = new ChatRepository(db);
+    authorId = new UserRepository(db).create({
+      name: 'A',
+      email: 'a@example.com',
+      passwordHash: 'h',
+    }).id;
+    projectId = new ProjectRepository(db).create({
+      name: 'P',
+      ownerId: authorId,
+    }).id;
+    new ProjectMemberRepository(db).add(projectId, authorId, 'admin');
+  });
+
+  afterEach(() => db.close());
+
+  it('creates and finds a message', () => {
+    const m = repo.create({ projectId, authorId, body: 'hello' });
+    expect(repo.findMessageById(m.id)?.body).toBe('hello');
+  });
+
+  it('lists messages newest first with total', () => {
+    repo.create({ projectId, authorId, body: 'first' });
+    repo.create({ projectId, authorId, body: 'second' });
+    const { items, total } = repo.findMessages(projectId);
+    expect(total).toBe(2);
+    expect(items[0].body).toBe('second');
+  });
+
+  it('excludes soft-deleted messages', () => {
+    const m = repo.create({ projectId, authorId, body: 'x' });
+    repo.delete(m.id);
+    expect(repo.findMessageById(m.id)).toBeNull();
+    expect(repo.findMessages(projectId).total).toBe(0);
+  });
+
+  it('isolates messages by project', () => {
+    repo.create({ projectId, authorId, body: 'mine' });
+    const p2 = new ProjectRepository(db).create({
+      name: 'P2',
+      ownerId: authorId,
+    }).id;
+    repo.create({ projectId: p2, authorId, body: 'theirs' });
+    expect(repo.findMessages(projectId).total).toBe(1);
+    expect(repo.findMessages(p2).total).toBe(1);
+  });
+
+  it('searches messages by body', () => {
+    repo.create({ projectId, authorId, body: 'hello world' });
+    repo.create({ projectId, authorId, body: 'goodbye' });
+    expect(repo.findMessages(projectId, { search: 'hello' }).total).toBe(1);
+    expect(repo.findMessages(projectId, { search: 'nope' }).total).toBe(0);
+  });
+
+  it('paginates messages', () => {
+    for (let i = 0; i < 5; i++)
+      repo.create({ projectId, authorId, body: `m${i}` });
+    expect(
+      repo.findMessages(projectId, { page: 1, pageSize: 2 }).items
+    ).toHaveLength(2);
+    expect(repo.findMessages(projectId, { page: 1, pageSize: 2 }).total).toBe(
+      5
+    );
+  });
+
+  it('updates a message body', () => {
+    const m = repo.create({ projectId, authorId, body: 'x' });
+    expect(repo.update(m.id, 'edited')?.body).toBe('edited');
+  });
+});