node:readline (+ cluster, http2, diagnostics_channel) — remaining core modules #31

Summary

node:readline and node:readline/promises are not implemented (no match in preludes/node_builtins.rs at a0c723e). The remaining unimplemented core modules are http2, cluster, inspector, v8, wasi, diagnostics_channel.

Why it matters

readline is the standard way to (a) read stdin line-by-line in CLIs and (b) stream large files with for await (const line of rl). Interactive prompts (inquirer, prompts, enquirer), REPL-style tools, and log processors all depend on it. With process.stdin and node:stream now present in 0.10.5, this is a small, high-leverage addition.

Proposal

Priority order:

1. readline — createInterface({ input, output, terminal }), question(), on('line'|'close'), async iterator, readline/promises. Pure-JS on top of existing node:stream + node:tty.
2. cluster — can be a thin facade over worker_threads / child_process.fork once async fork exists; isPrimary, fork(), workers, on('exit').
3. http2 — larger; at minimum http2.connect client for gRPC-style consumers, server later.
4. diagnostics_channel — trivial pub/sub, used by undici, fastify, OpenTelemetry instrumentation.
5. inspector, v8, wasi — document as intentionally unsupported in a compatibility matrix rather than leaving them to Cannot find module.