feat: replace subagent and skills with unified summon extension (#6964)

Signed-off-by: Travis Longwell <travis@block.xyz>

crates/goose/src/agents/execute_commands.rs

@@ -378,7 +378,7 @@ impl Agent {
             Err(e) => return Err(anyhow!("Failed to build recipe: {}", e)),
         };
 
-        self.apply_recipe_components(recipe.sub_recipes.clone(), recipe.response.clone(), true)
+        self.apply_recipe_components(recipe.response.clone(), true)
             .await;
 
         let prompt = [recipe.instructions.as_deref(), recipe.prompt.as_deref()]