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/transport.ts

@@ -0,0 +1,18 @@
+export interface ByteTransport {
+	/** Sends one byte chunk. Calls must be delivered in invocation order. */
+	send(chunk: Uint8Array): Promise<void>;
+	/** Closes the transport. Implementations must make repeated calls harmless. */
+	close(): void;
+}
+
+export interface ByteTransportHandlers {
+	/** Delivers an arbitrary inbound byte chunk. */
+	onData(chunk: Uint8Array): void;
+	/** Reports an orderly terminal close. */
+	onClose(): void;
+	/** Reports a terminal transport failure. */
+	onError(error: Error): void;
+}
+
+/** Creates a fresh connected, authenticated transport. Exactly one terminal handler is expected. */
+export type ByteTransportFactory = (handlers: ByteTransportHandlers) => ByteTransport | Promise<ByteTransport>;