Default to Sonnet 4.5 in BYOK (#39132)

<img width="381" height="204" alt="Screenshot 2025-09-29 at 2 29 58 PM"
src="https://github.com/user-attachments/assets/c7aaf0b0-b09b-4ed9-8113-8d7b18eefc2f"
/>


Release Notes:

- Claude Sonnet 4.5 and 4.5 Thinking are now the recommended Anthropic
models

crates/language_models/src/provider/anthropic.rs

@@ -151,8 +151,8 @@ impl LanguageModelProvider for AnthropicLanguageModelProvider {
 
     fn recommended_models(&self, _cx: &App) -> Vec<Arc<dyn LanguageModel>> {
         [
-            anthropic::Model::ClaudeSonnet4,
-            anthropic::Model::ClaudeSonnet4Thinking,
+            anthropic::Model::ClaudeSonnet4_5,
+            anthropic::Model::ClaudeSonnet4_5Thinking,
         ]
         .into_iter()
         .map(|model| self.create_language_model(model))