// Minimal repro for task #128 (residual phenom external-port LTS
// divergence: ActiveHolderNavigationImpl / PStageControlLoadingArbiter).
//
// An `external` requires port with a request/response pattern
// (doit -> done out-event, bounded so the queue never overflows) PLUS
// a synchronous nondeterministic-reply query (`status`, returns
// bool, always callable, no iface state change). The component calls
// `status` in a reply-gated chain WHILE `done` is pending (the
// external spontaneous group is enabled).
//
// BUG: ours's `__fire__` (pre/post-call external-spontaneous) path
// emits spurious `tau` edges at the post-call state to per-reply
// committed states, turning the requires-reply into an INTERNAL
// choice (tau-fork: each stable state offers only one of
// {e.true,e.false}). dzn's golden (post-fork) offers BOTH replies
// from one state — EXTERNAL choice. Under weak-failures these differ
// (internal can refuse a single reply; external cannot), so ours is
// not <= the golden.
//
// Clean baseline: pre-branch ours == raw dzn (both internal here);
// the divergence is new-engine vs post-fork golden. The fix makes the
// __fire__ path keep the reply external (offered from the shared
// post-call state), matching the inline requires-call path and the
// golden. See memory project_external_real_bug + step_frontier.rs
// AwaitingExternalSpontaneous handling (~L2785-2974, the __fire__
// tau at L2823).
//
// xfail until the engine fix lands.
