ACP champagne (#35609)

cherry pick changes from #35510 onto latest main

Release Notes:

- N/A

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Lukas Wirth <lukas@zed.dev>

crates/agent_ui/Cargo.toml

@@ -19,6 +19,7 @@ test-support = ["gpui/test-support", "language/test-support"]
 acp_thread.workspace = true
 agent-client-protocol.workspace = true
 agent.workspace = true
+agent2.workspace = true
 agent_servers.workspace = true
 agent_settings.workspace = true
 ai_onboarding.workspace = true