chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/packages/durable/test/heap-retained.ts

@@ -0,0 +1,26 @@
+// For benchmarks: the bytes live objects hold, from a heap snapshot. `heapUsed` after `gc()` also counts what the
+// collector has not compacted yet, which hides a small leak or invents a large one.
+import { Session } from "node:inspector/promises";
+
+/** Sum of the self sizes of every object in a fresh heap snapshot, which collects garbage first. */
+export async function retainedBytes(): Promise<number> {
+	const inspector = new Session();
+	inspector.connect();
+	const chunks: string[] = [];
+	inspector.on("HeapProfiler.addHeapSnapshotChunk", (message) => chunks.push(message.params.chunk));
+	try {
+		await inspector.post("HeapProfiler.takeHeapSnapshot", { reportProgress: false });
+	} finally {
+		inspector.disconnect();
+	}
+	const snapshot = JSON.parse(chunks.join("")) as {
+		snapshot: { meta: { node_fields: string[] } };
+		nodes: number[];
+	};
+	const fields = snapshot.snapshot.meta.node_fields;
+	const width = fields.length;
+	const size = fields.indexOf("self_size");
+	let total = 0;
+	for (let index = size; index < snapshot.nodes.length; index += width) total += snapshot.nodes[index]!;
+	return total;
+}