feat: add template setup executable support

Templates can now include a `setup` file that runs in the workdir
before agent execution starts. Used for workspace initialization
like pulling tool binaries or installing dependencies.

src/agent.rs

@@ -327,6 +327,22 @@ async fn agent_loop(
                 ensure_workspace(&exec, &workdir).await;
                 let _ = tokio::fs::write(format!("{}/requirement.md", workdir), &requirement).await;
 
+                // Run template setup if present
+                if let Some(ref tid) = template_id {
+                    let template_dir = if template::is_repo_template(tid) {
+                        template::extract_repo_template(tid, mgr.template_repo.as_ref())
+                            .await
+                            .ok()
+                    } else {
+                        Some(std::path::Path::new(template::templates_dir()).join(tid))
+                    };
+                    if let Some(ref tdir) = template_dir {
+                        if let Err(e) = template::run_setup(tdir, &workdir).await {
+                            tracing::error!("Template setup failed for {}: {}", tid, e);
+                        }
+                    }
+                }
+
                 let instructions = if let Some(ref t) = loaded_template {
                     t.instructions.clone()
                 } else {