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/acp_thread/Cargo.toml

@@ -25,6 +25,7 @@ futures.workspace = true
 gpui.workspace = true
 itertools.workspace = true
 language.workspace = true
+language_model.workspace = true
 markdown.workspace = true
 project.workspace = true
 serde.workspace = true