refactor: remove agent flavours, move provider to Agent (#2091)

crates/goose/examples/agent.rs

@@ -1,6 +1,8 @@
+use std::sync::Arc;
+
 use dotenv::dotenv;
 use futures::StreamExt;
-use goose::agents::{AgentFactory, ExtensionConfig};
+use goose::agents::{Agent, ExtensionConfig};
 use goose::config::{DEFAULT_EXTENSION_DESCRIPTION, DEFAULT_EXTENSION_TIMEOUT};
 use goose::message::Message;
 use goose::providers::databricks::DatabricksProvider;
@@ -10,10 +12,10 @@ async fn main() {
     // Setup a model provider from env vars
     let _ = dotenv();
 
-    let provider = Box::new(DatabricksProvider::default());
+    let provider = Arc::new(DatabricksProvider::default());
 
     // Setup an agent with the developer extension
-    let mut agent = AgentFactory::create("reference", provider).expect("default should exist");
+    let mut agent = Agent::new(provider);
 
     let config = ExtensionConfig::stdio(
         "developer",