agent-client-protocol-v0.8.0

The types from the Rust crate, agent-client-protocol-schema has major breaking changes. All exported type are now marked as #[non_exhaustive]. Since the schema itself is JSON, and we can introduce new fields and variants in a non-breaking way, we wanted to allow for the same behavior in the Rust library.

All enum variants are also tuple variants now, with their own structs. This made it nicer to represent in the JSON Schema, and also made sure we have _meta fields on all variants.

This upgrade will likely come with a lot of compilation errors, but ideally upgrading will be more painless in the future.