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/telemetry/CHANGELOG.md

@@ -0,0 +1,19 @@
+# Changelog
+
+## [0.85.1] - 2026-09-05
+
+## [0.85.0] - 2026-09-04
+
+## [0.84.4] - 2026-08-28
+
+## [0.84.3] - 2026-08-24
+
+## [0.84.2] - 2026-08-14
+
+## [0.84.1] - 2026-08-07
+
+## [0.84.0] - 2026-08-06
+
+### Added
+
+- Added the callback-based telemetry context contract, shared no-op context, deterministic in-memory reference adapter, reusable adapter conformance suite, typed serializable schema utilities, and multi-schema typed span starters with explicit child propagation.