Fix：补全 SQL Server IDENTITY_INSERT 关键字

[zipg]

修复内容

• 在 SQL Server 专属补全关键字中加入 IDENTITY_INSERT
• 补充常用 SQL Server SET 选项补全，包括 NOCOUNT、XACT_ABORT、ANSI_*、QUOTED_IDENTIFIER、STATISTICS IO/TIME/XML 等
• 增加 set iden 以及常用 SET 选项输入场景的回归测试

验证

• pnpm vitest run packages/app-tests/sqlCompletion.test.ts -t "suggests SQL Server IDENTITY_INSERT after SET"
• pnpm vitest run packages/app-tests/sqlCompletion.test.ts
• pnpm fmt

[t8y2]

Thanks for the contribution! Merged in 3e9c6c4, will be released in the next version.