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/chord/test/helpers.ts

@@ -0,0 +1 @@
+export { createLoopbackServiceTransport } from "../src/services/loopback.ts";