assistant: Add health telemetry (#19928)

This PR adds a bit of telemetry for Anthropic models, in order to
understand model health. With this logging, we can monitor and diagnose
dips in performance, for example due to model rollouts.

Release Notes:

- N/A

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/language_model/src/provider/anthropic.rs

@@ -26,7 +26,7 @@ use theme::ThemeSettings;
 use ui::{prelude::*, Icon, IconName, Tooltip};
 use util::{maybe, ResultExt};
 
-const PROVIDER_ID: &str = "anthropic";
+pub const PROVIDER_ID: &str = "anthropic";
 const PROVIDER_NAME: &str = "Anthropic";
 
 #[derive(Default, Clone, Debug, PartialEq)]
@@ -356,6 +356,10 @@ impl LanguageModel for AnthropicModel {
         format!("anthropic/{}", self.model.id())
     }
 
+    fn api_key(&self, cx: &AppContext) -> Option<String> {
+        self.state.read(cx).api_key.clone()
+    }
+
     fn max_token_count(&self) -> usize {
         self.model.max_token_count()
     }
@@ -520,6 +524,14 @@ pub fn map_to_language_model_completion_events(
                                 ));
                             }
                         }
+                        Event::MessageStart { message } => {
+                            return Some((
+                                Some(Ok(LanguageModelCompletionEvent::StartMessage {
+                                    message_id: message.id,
+                                })),
+                                state,
+                            ))
+                        }
                         Event::MessageDelta { delta, .. } => {
                             if let Some(stop_reason) = delta.stop_reason.as_deref() {
                                 let stop_reason = match stop_reason {