feat(core): programs' threads, and FILIUS' echo server and generic client after Java, measured against Java

Programs run as generators that yield what they wait for (threads.ts); the
engine resumes them after every event. TCP connect, send, receive, accept
and name resolution exist as such steps; the blocking calls wrap them.
EchoRun records eight stories in Java FILIUS, frames, tables and each
program's window lines; echoJava.test.ts plays them card by card. Not
taken from Java: a connection without a route hangs for ever; a server
switched off leaves its connections' last FIN unanswered.

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

packages/core/src/index.ts

@@ -17,6 +17,9 @@ export * from './runtime/speed.js';
 export * from './runtime/trace.js';
 export * from './runtime/capture.js';
 export * from './runtime/captureRows.js';
+export * from './runtime/threads.js';
+export * from './runtime/apps/program.js';
+export * from './runtime/apps/echo.js';
 export * from './util/equal.js';
 export * from './util/javaIp.js';
 export * from './util/swiftString.js';