feat(cli): add /bug-memory command and auto-capture heap snapshot in /bug (#25639)

packages/cli/src/ui/utils/memorySnapshot.ts

@@ -0,0 +1,30 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { createWriteStream } from 'node:fs';
+import { mkdir } from 'node:fs/promises';
+import { dirname } from 'node:path';
+import { pipeline } from 'node:stream/promises';
+import { getHeapSnapshot } from 'node:v8';
+
+/**
+ * RSS threshold at which `/bug` auto-captures a heap snapshot.
+ */
+export const MEMORY_SNAPSHOT_AUTO_THRESHOLD_BYTES = 2 * 1024 * 1024 * 1024;
+
+/**
+ * Capture a V8 heap snapshot from the current process and write it to disk.
+ *
+ * `v8.getHeapSnapshot()` returns a Readable stream whose producer is V8's
+ * internal snapshot generator. Piping it through `node:stream/promises`'
+ * `pipeline` propagates backpressure end-to-end, so even a multi-gigabyte
+ * heap is written without buffering the serialized snapshot in memory.
+ * Nothing is exposed over a debugger port.
+ */
+export async function captureHeapSnapshot(filePath: string): Promise<void> {
+  await mkdir(dirname(filePath), { recursive: true });
+  await pipeline(getHeapSnapshot(), createWriteStream(filePath));
+}