feat(core): the e-mail program after Java, measured against Java

The program sends to its account's SMTP server, one connection for each
recipient, and fetches its mails by POP3; the server now sends mails on
to other domains by MX and returns notices to their senders. The
program's folders are in the snapshot and go back into the project.
EmailClientRun plays six stories with two servers; the mail oracles run
in the language's locale, so Java's notice dates match the core's.

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

packages/core/src/index.ts

@@ -25,6 +25,7 @@ export * from './runtime/apps/web.js';
 export * from './runtime/apps/routerPages.js';
 export * from './runtime/apps/firewallSettings.js';
 export * from './runtime/apps/emailServer.js';
+export * from './runtime/apps/emailClient.js';
 export * from './runtime/email.js';
 export * from './runtime/http.js';
 export * from './util/equal.js';