Fix: Correct message part ordering in A2A history

The previous logic iterated through session events in reverse and then
reversed the resulting list of parts. This caused incorrect ordering for
multi-part messages generated by `_present_other_agent_message`.

Specifically, introductory text like "For context:" was appearing after
the content it was meant to introduce.

This change simplifies the implementation by removing both reversals. It now
processes events in chronological order, ensuring all message parts are
appended in the correct sequence.

Signed-off-by: Eran Cohen <eranco@redhat.com>

Author: eranco74

src/google/adk/agents/remote_a2a_agent.py

@@ -356,7 +356,7 @@ def _construct_message_parts_from_session(
     """
     message_parts: list[A2APart] = []
     context_id = None
-    for event in reversed(ctx.session.events):
+    for event in ctx.session.events:
       if _is_other_agent_reply(self.name, event):
         event = _present_other_agent_message(event)
       elif event.author == self.name:
@@ -378,7 +378,7 @@ def _construct_message_parts_from_session(
         else:
           logger.warning("Failed to convert part to A2A format: %s", part)
 
-    return message_parts[::-1], context_id
+    return message_parts, context_id
 
   async def _handle_a2a_response(
       self, a2a_response: A2AClientEvent | A2AMessage, ctx: InvocationContext