Enable runtime access to provider name (#5399)

crates/goose/src/agents/reply_parts.rs

@@ -309,6 +309,10 @@ mod tests {
             crate::providers::base::ProviderMetadata::empty()
         }
 
+        fn get_name(&self) -> &str {
+            "mock"
+        }
+
         fn get_model_config(&self) -> ModelConfig {
             self.model_config.clone()
         }