createTestHarness: first RPC call that creates a Workflow deadlocks Node.js (since miniflare 5.20260820.0-alpha)

Finding: In an externally reported regression, a Worker started with createTestHarness() hangs the Node.js process on the first RPC call that creates a Workflow (env.MY_WORKFLOW.create() inside a WorkerEntrypoint method called via getWorker().getExport()). The reporter says this affects wrangler 4.125.0 through 4.149.0 (miniflare 5.20260820.0-alpha through 5.20261006.1-alpha) on Node 22.21.1 (macOS arm64) and 22.22.0 (Linux x86_64), while wrangler 4.124.0 (miniflare 5.20260815.0-alpha) passes [https://github.com/cloudflare/workers-sdk/issues/16181]. Symptom: the call never returns and the Node main thread stays blocked, so timers, Vitest hook timeouts and test timeouts never fire. No error message is logged; the output stops after the 'calling startWorkflow()...' line [https://github.com/cloudflare/workers-sdk/issues/16181]. Reporter's hypothesized cause (not maintainer-confirmed): the Node RPC proxy makes the first call to each method synchronous, blocking the main thread with Atomics.wait until workerd replies. A Workflow-deletion change reportedly added a service loopback binding to each Workflow engine, and that loopback server runs on the blocked main thread, so neither side can proceed. The reporter says a stack trace showed the synchronous call path, and that removing only the loopback binding from miniflare 5.20260820.0-alpha made the call return [https://github.com/cloudflare/workers-sdk/issues/16181]. Reported version matrix: wrangler 4.124.0 passes with both workerd 1.20260815.1 and a 1.20260820.1 override; wrangler 4.125.0 with miniflare overridden to 5.20260815.0-alpha passes; wrangler 4.125.0 with miniflare 5.20260820.0-alpha hangs; wrangler 4.149.0 with miniflare 5.20261006.1-alpha hangs [https://github.com/cloudflare/workers-sdk/issues/16181]. An automated, LLM-generated triage comment says it reproduced the hang on wrangler 4.149.0: the process needed an external SIGKILL, and the same fixture passed on 4.124.0 [https://github.com/cloudflare/workers-sdk/issues/16181#issuecomment-6082918183]. Treat this as another external report, not independent verification. Status: the issue is open. The reporter lists possible fixes (async call for WorkerEntrypoint stubs, avoiding the loopback until deletion, or serving the loopback off the blocked thread), but these are proposals only. No fix commit or released fix appears in the supplied sources. Limitations: this is an external report, and there was no KFA reproduction. The cause is unconfirmed by maintainers, and comment coverage may be incomplete.