atproto 是做什么的？
Migrate AT Protocol client and consumer code off the legacy @atproto/api, @atproto/lexicon, and @atproto/xrpc stack onto @atproto/lex. Use whenever code that calls out to an XRPC service is being modernized — replacing an AtpAgent with Client, result.data / result.headers[…] response handling, XRPCError try/catch, jsonStringToLex / stringifyLex, BlobRef instanceof checks, CID from multiformats, new Date().toISOString() on AT Proto datetimes, bare string DIDs a