Reverts commits47b5e45,5c76939,1eecae0,660208a,86a9f65,259d5b6. Removes PinnedPropertiesBar, usePinnedProperties hook, Rust backend for _pinned_properties, and all related tests. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>