fix(runtime): keep a rejecting fire-and-forget verb from killing the script

src/runtime.mjs

@@ -59,12 +59,19 @@ function makeControl(max, out) {
 // otherwise the process could exit before a fire-and-forget notification lands.
 // Blocking verbs (the CLI verbs via spawnSync, sleep) return synchronously and
 // need no draining, which is what keeps the simple no-`await` style correct.
+//
+// What gets queued is `Promise.allSettled([result])`, not the bare `result`. The
+// settled wrapper subscribes immediately, so a fire-and-forget verb that rejects
+// is never seen as an unhandled rejection while the script runs on — queueing the
+// bare promise let Node kill the process at the next tick, before the drain below
+// could ever observe it. The script still gets the original promise back, so an
+// `await`ed call fails exactly as before.
 function makeScope(registry, ctx, control, pending) {
   const bound = new Map();
   for (const cmd of registry.all()) {
     bound.set(cmd.name, (...args) => {
       const result = cmd.run(ctx, ...args);
-      if (result && typeof result.then === "function") pending.push(result);
+      if (result && typeof result.then === "function") pending.push(Promise.allSettled([result]));
       return result;
     });
   }

test/runtime.test.mjs

@@ -111,3 +111,27 @@ test("DEFAULT_MAX bounds an unbounded while when no max is passed", async () =>
   await runScript(`while (alive) { push(1); }`, { commands: registry });
   assert.equal(calls.length, DEFAULT_MAX);
 });
+
+test("a rejecting fire-and-forget verb does not kill a script that keeps running", async () => {
+  const calls = [];
+  const registry = createRegistry([
+    { name: "push", summary: "record", run: (_ctx, x) => calls.push(x) },
+    { name: "fire", summary: "async, rejects", run: async () => { throw new Error("network boom"); } },
+    { name: "waitv", summary: "async, resolves later", run: (_ctx, ms) => new Promise((r) => setTimeout(r, ms)) },
+  ]);
+  // The rejection must stay observed from the moment it is queued: crossing a
+  // tick boundary (the `await waitv`) used to let Node report it as unhandled
+  // and tear the process down before the drain in runScript ran.
+  const result = await runScript(`fire(); await waitv(5); push("after wait");`, {
+    commands: registry,
+  });
+  assert.deepEqual(calls, ["after wait"]);
+  assert.deepEqual(result, { iterations: 0, stopped: false });
+});
+
+test("an awaited async verb still propagates its rejection to the script", async () => {
+  const registry = createRegistry([
+    { name: "fire", summary: "async, rejects", run: async () => { throw new Error("network boom"); } },
+  ]);
+  await assert.rejects(async () => runScript(`await fire();`, { commands: registry }), /network boom/);
+});