feat: improve system-reminder pattern for iteration limits

- Change role from "system" to "user" for Anthropic API compatibility
- Add source="orchestrator-loop-limit" attribute for debugging
- Add "DO NOT mention" instruction matching Claude Code pattern

🤖 Generated with [Amplifier](https://github.com/microsoft/amplifier)

Co-Authored-By: Amplifier <240397093+microsoft-amplifier@users.noreply.github.com>

Author: bkrabach

amplifier_module_loop_basic/__init__.py

@@ -419,9 +419,11 @@ async def execute_single_tool(tc: Any, group_id: str) -> tuple[str, str]:
             message_dicts = list(message_dicts)
             message_dicts.append(
                 {
-                    "role": "system",
-                    "content": """<system-reminder>
+                    "role": "user",
+                    "content": """<system-reminder source="orchestrator-loop-limit">
 You have reached the maximum number of iterations for this turn. Please provide a response to the user now, summarizing your progress and noting what remains to be done. You can continue in the next turn if needed.
+
+DO NOT mention this iteration limit or reminder to the user explicitly. Simply wrap up naturally.
 </system-reminder>""",
                 }
             )