chore(vendor): import pi 0.85.1

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: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/ai/src/utils/abort.ts

@@ -0,0 +1,50 @@
+function abortReason(signal: AbortSignal): unknown {
+	if (signal.reason !== undefined) return signal.reason;
+	const error = new Error("The operation was aborted");
+	error.name = "AbortError";
+	return error;
+}
+
+/** Create an operation-local signal for public APIs whose signal is optional. */
+export function operationSignal(signal?: AbortSignal): AbortSignal {
+	return signal ?? new AbortController().signal;
+}
+
+/**
+ * Stop waiting for an operation when its signal aborts while continuing to
+ * observe the abandoned promise so a later rejection is always handled.
+ */
+export function raceWithAbortSignal<T>(operation: Promise<T>, signal: AbortSignal): Promise<T> {
+	if (signal.aborted) {
+		void operation.catch(() => {});
+		return Promise.reject(abortReason(signal));
+	}
+
+	return new Promise<T>((resolve, reject) => {
+		let settled = false;
+		const cleanup = () => signal.removeEventListener("abort", onAbort);
+		const onAbort = () => {
+			if (settled) return;
+			settled = true;
+			cleanup();
+			reject(abortReason(signal));
+		};
+
+		signal.addEventListener("abort", onAbort, { once: true });
+		void operation.then(
+			(value) => {
+				if (settled) return;
+				settled = true;
+				cleanup();
+				resolve(value);
+			},
+			(error: unknown) => {
+				if (settled) return;
+				settled = true;
+				cleanup();
+				reject(error);
+			},
+		);
+		if (signal.aborted) onAbort();
+	});
+}