chore(unstable): Start setting up v2 Schema scaffolding for experimentation (#1099)

* initial

* cleanups

* Cleanups

* Docs

* Shared RPC types

* Remove unneeded method name conversions

Author: benbrandt

AGENTS.md

@@ -19,7 +19,7 @@ All paths in the protocol should be absolute
 
 - Add constants for the method names
 - Add variants to {Agent|Client}{Request|Response} enums
-- Add the method to markdown_generator.rs SideDocs functions
+- Add the method to src/bin/generate.rs SideDocs functions
 - Run `npm run generate` and fix any issues that appear
 - Run `npm run check`
 - Update the example agents and clients in tests and examples in both libraries

Cargo.toml

@@ -28,6 +28,11 @@ unstable = [
     "unstable_message_id",
     "unstable_boolean_config",
 ]
+# Protocol v2 is intentionally NOT part of the `unstable` umbrella.
+# It introduces a parallel `v2` module and (eventually) a different wire
+# version, so it must be opted into explicitly to avoid silently
+# changing `ProtocolVersion::LATEST` for `unstable` users.
+unstable_protocol_v2 = []
 unstable_auth_methods = []
 unstable_cancel_request = []
 unstable_elicitation = []