AI 小说工坊：主编 + 作家多模型协作写作应用

- Nuxt 4 + Nuxt UI 4 + AI SDK 7 + Drizzle/SQLite
- 主编规划大纲与章节简报、选派作家；作家流式写入章节文件并实时推送前端
- 逐章确认模式（默认）与自动模式；摘要与故事记忆
- 酒馆角色卡（PNG/JSON，V1-V3）与世界书导入
- 自定义最高优先级系统提示词、审稿/修改/多版本、任务日志与提示词检视
- 模拟 LLM 服务与端到端测试脚本

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/utils/db.ts

@@ -0,0 +1,38 @@
+import { mkdirSync, existsSync } from 'node:fs'
+import { join, resolve } from 'node:path'
+import Database from 'better-sqlite3'
+import { drizzle, type BetterSQLite3Database } from 'drizzle-orm/better-sqlite3'
+import { migrate } from 'drizzle-orm/better-sqlite3/migrator'
+import * as schema from '../db/schema'
+
+export { schema }
+export const tables = schema
+
+let _db: BetterSQLite3Database<typeof schema> | null = null
+
+export function dataDir() {
+  // 运行时读取环境变量（runtimeConfig 的默认值在构建时就已固定）
+  const dir = resolve(process.env.NOVEL_DATA_DIR || useRuntimeConfig().dataDir || './data')
+  if (!existsSync(dir)) mkdirSync(dir, { recursive: true })
+  return dir
+}
+
+function migrationsFolder() {
+  const candidates = [
+    resolve(process.cwd(), 'server/db/migrations'),
+    resolve(process.cwd(), '../server/db/migrations')
+  ]
+  const found = candidates.find(p => existsSync(join(p, 'meta', '_journal.json')))
+  if (!found) throw new Error('找不到数据库迁移目录 server/db/migrations，请在项目根目录启动应用')
+  return found
+}
+
+export function useDb() {
+  if (_db) return _db
+  const sqlite = new Database(join(dataDir(), 'app.db'))
+  sqlite.pragma('journal_mode = WAL')
+  sqlite.pragma('foreign_keys = ON')
+  _db = drizzle({ client: sqlite, schema })
+  migrate(_db, { migrationsFolder: migrationsFolder() })
+  return _db
+}