Track cumulative token usage in assistant2 when using anthropic API (#26738)

Release Notes:

- N/A

crates/language_models/Cargo.toml

@@ -33,6 +33,7 @@ gpui_tokio.workspace = true
 http_client.workspace = true
 language_model.workspace = true
 lmstudio = { workspace = true, features = ["schemars"] }
+log.workspace = true
 menu.workspace = true
 mistral = { workspace = true, features = ["schemars"] }
 ollama = { workspace = true, features = ["schemars"] }