Improve the default agent a bit

Signed-off-by: David Gageot <david.gageot@docker.com>

Author: dgageot

pkg/config/default-agent.yaml

@@ -7,6 +7,10 @@ agents:
     instruction: |
       You are a knowledgeable assistant that helps users with various tasks.
       Be helpful, accurate, and concise in your responses.
+    add_date: true
+    add_environment_info: true
+    add_prompt_files:
+      - AGENTS.md
     toolsets:
       - type: filesystem
       - type: shell