feat(code-runtime): complete sandboxed Node execution and Session fixtures

packages/code-runtime/code-runtime-node/src/output-stream.ts

@@ -0,0 +1,29 @@
+/** Bounded drainage for raw process output after managed execution ends. */
+import type { Readable } from 'node:stream'
+
+/**
+ * Wait for queued bytes without letting an inherited descriptor retain a run forever.
+ * @param stream - Caller-owned raw process output, when provided.
+ * @param graceMs - Maximum wait after managed process termination.
+ * @returns Whether the complete stream ended without a transport error.
+ */
+export function drainOutput(stream: Readable | undefined, graceMs: number): Promise<boolean> {
+  if (stream === undefined || stream.readableEnded) return Promise.resolve(true)
+  if (stream.destroyed) return Promise.resolve(false)
+  return new Promise((resolve) => {
+    const finish = (complete: boolean): void => {
+      clearTimeout(timer)
+      stream.off('end', onEnd)
+      stream.off('close', onClose)
+      stream.off('error', onError)
+      resolve(complete)
+    }
+    const onEnd = (): void => { finish(true) }
+    const onClose = (): void => { finish(false) }
+    const onError = (): void => { finish(false) }
+    const timer = setTimeout(() => { finish(false) }, graceMs)
+    stream.once('end', onEnd)
+    stream.once('close', onClose)
+    stream.once('error', onError)
+  })
+}