anthropic: Add support for Claude 4 (#31203)

This PR adds support for [Claude
4](https://www.anthropic.com/news/claude-4).

Release Notes:

- Added support for Claude Opus 4 and Claude Sonnet 4.

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>

crates/language_model/src/language_model.rs

@@ -16,7 +16,6 @@ use gpui::{AnyElement, AnyView, App, AsyncApp, SharedString, Task, Window};
 use http_client::http::{HeaderMap, HeaderValue};
 use icons::IconName;
 use parking_lot::Mutex;
-use proto::Plan;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize, de::DeserializeOwned};
 use std::fmt;
@@ -48,15 +47,6 @@ pub fn init_settings(cx: &mut App) {
     registry::init(cx);
 }
 
-/// The availability of a [`LanguageModel`].
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
-pub enum LanguageModelAvailability {
-    /// The language model is available to the general public.
-    Public,
-    /// The language model is available to users on the indicated plan.
-    RequiresPlan(Plan),
-}
-
 /// Configuration for caching language model messages.
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize, JsonSchema)]
 pub struct LanguageModelCacheConfiguration {
@@ -242,11 +232,6 @@ pub trait LanguageModel: Send + Sync {
         None
     }
 
-    /// Returns the availability of this language model.
-    fn availability(&self) -> LanguageModelAvailability {
-        LanguageModelAvailability::Public
-    }
-
     /// Whether this model supports images
     fn supports_images(&self) -> bool;