Update foundational examples to use "user" role

Use system_instruction on LLM service constructors instead of adding
system messages to LLMContext. Messages added to context now use
"user" role.

examples/foundational/26b-gemini-live-function-calling.py

@@ -131,13 +131,7 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     # than as arguments to GeminiLiveLLMService, but note that doing so will
     # trigger a (fast) reconnection when the GeminiLiveLLMService first
     # receives the context (i.e. when we send the LLMRunFrame below).
-    context = LLMContext(
-        [
-            # {"role": "system", "content": system_instruction},
-            {"role": "user", "content": "Say hello."},
-        ],
-        # tools,
-    )
+    context = LLMContext()
     user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
         context,
         user_params=LLMUserAggregatorParams(
@@ -172,6 +166,7 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     async def on_client_connected(transport, client):
         logger.info(f"Client connected")
         # Kick off the conversation.
+        context.add_message({"role": "user", "content": "Please introduce yourself to the user."})
         await task.queue_frames([LLMRunFrame()])
 
     @transport.event_handler("on_client_disconnected")