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/client/src/index.ts

@@ -0,0 +1,12 @@
+export { Client, createClientServiceTransport } from "./client.ts";
+export { ClientDisposedError, DisconnectedError, ServerError } from "./errors.ts";
+export type { ByteTransport, ByteTransportFactory, ByteTransportHandlers } from "./transport.ts";
+export type {
+	AttachmentChangeListener,
+	ClientOptions,
+	ConnectionState,
+	ConnectionStateChange,
+	ListenerErrorHandler,
+	ServiceSubscription,
+	Unsubscribe,
+} from "./types.ts";