Add agents package with Flue

packages/agents/src/agents/hello-world.ts

@@ -0,0 +1,6 @@
+import { defineAgent } from '@flue/runtime';
+
+export default defineAgent(() => ({
+  model: 'anthropic/claude-sonnet-4-6',
+  instructions: 'Give a concise, helpful hello-world response for this project.',
+}));