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)

repositories/ChatRepository.ts

@@ -0,0 +1,129 @@
+import type { SqliteDatabase } from '@/lib/db/sqlite';
+import type { ChatMessage } from '@/lib/types';
+
+const DEFAULT_PAGE_SIZE = 20;
+
+export interface Paginated<T> {
+  items: T[];
+  total: number;
+}
+
+interface ChatMessageRow {
+  id: number;
+  project_id: number;
+  author_id: number;
+  body: string;
+  created_at: string;
+  updated_at: string;
+  deleted_at: string | null;
+}
+
+function mapMessage(row: ChatMessageRow): ChatMessage {
+  return {
+    id: row.id,
+    projectId: row.project_id,
+    authorId: row.author_id,
+    body: row.body,
+    createdAt: row.created_at,
+    updatedAt: row.updated_at,
+    deletedAt: row.deleted_at,
+  };
+}
+
+export interface ListMessagesOptions {
+  page?: number;
+  pageSize?: number;
+  search?: string;
+}
+
+export class ChatRepository {
+  constructor(private readonly db: SqliteDatabase) {}
+
+  findMessages(
+    projectId: number,
+    opts: ListMessagesOptions = {}
+  ): Paginated<ChatMessage> {
+    const page = opts.page ?? 1;
+    const pageSize = opts.pageSize ?? DEFAULT_PAGE_SIZE;
+    const offset = (page - 1) * pageSize;
+    const search = opts.search?.trim();
+
+    if (search) {
+      const like = `%${search}%`;
+      const items = this.db.query<ChatMessageRow>(
+        `SELECT * FROM chat_messages
+         WHERE project_id = @projectId AND deleted_at IS NULL
+           AND body LIKE @like
+         ORDER BY created_at DESC, id DESC
+         LIMIT @pageSize OFFSET @offset`,
+        { projectId, like, pageSize, offset }
+      );
+      const total = this.db.get<{ count: number }>(
+        `SELECT COUNT(*) AS count FROM chat_messages
+         WHERE project_id = @projectId AND deleted_at IS NULL AND body LIKE @like`,
+        { projectId, like }
+      );
+      return { items: items.map(mapMessage), total: total?.count ?? 0 };
+    }
+
+    const items = this.db.query<ChatMessageRow>(
+      `SELECT * FROM chat_messages
+       WHERE project_id = @projectId AND deleted_at IS NULL
+       ORDER BY created_at DESC, id DESC
+       LIMIT @pageSize OFFSET @offset`,
+      { projectId, pageSize, offset }
+    );
+    const total = this.db.get<{ count: number }>(
+      'SELECT COUNT(*) AS count FROM chat_messages WHERE project_id = @projectId AND deleted_at IS NULL',
+      { projectId }
+    );
+    return { items: items.map(mapMessage), total: total?.count ?? 0 };
+  }
+
+  findMessageById(id: number): ChatMessage | null {
+    const row = this.db.get<ChatMessageRow>(
+      'SELECT * FROM chat_messages WHERE id = @id AND deleted_at IS NULL',
+      { id }
+    );
+    return row ? mapMessage(row) : null;
+  }
+
+  create(input: {
+    projectId: number;
+    authorId: number;
+    body: string;
+  }): ChatMessage {
+    const now = new Date().toISOString();
+    const result = this.db.execute(
+      `INSERT INTO chat_messages (project_id, author_id, body, created_at, updated_at, deleted_at)
+       VALUES (@projectId, @authorId, @body, @createdAt, @updatedAt, NULL)`,
+      {
+        projectId: input.projectId,
+        authorId: input.authorId,
+        body: input.body,
+        createdAt: now,
+        updatedAt: now,
+      }
+    );
+    const created = this.findMessageById(Number(result.lastInsertRowid));
+    if (!created) throw new Error('Failed to create chat message');
+    return created;
+  }
+
+  update(id: number, body: string): ChatMessage | null {
+    this.db.execute(
+      `UPDATE chat_messages SET body = @body, updated_at = @updatedAt
+       WHERE id = @id AND deleted_at IS NULL`,
+      { body, updatedAt: new Date().toISOString(), id }
+    );
+    return this.findMessageById(id);
+  }
+
+  delete(id: number): boolean {
+    const result = this.db.execute(
+      'UPDATE chat_messages SET deleted_at = @now WHERE id = @id AND deleted_at IS NULL',
+      { now: new Date().toISOString(), id }
+    );
+    return result.changes > 0;
+  }
+}