Update assistant_id on each connection

It doesn't make any sense to require that this value be specified on
connect but then ignore it if the agent is already running. Let's put
the responsibility of ensuring that any change to an assistant ID is
appropriate on the client application rather than forcing the client
application to jump through unnecessary hoops to update the value
separately from the connection request.

lib/gpt_agent.ex

@@ -458,7 +458,7 @@ defmodule GptAgent do
 
       case Registry.lookup(GptAgent.Registry, opts.thread_id) do
         [{pid, :gpt_agent}] ->
-          handle_existing_agent(pid, opts.last_message_id)
+          handle_existing_agent(pid, opts.last_message_id, opts.assistant_id)
 
         [] ->
           handle_no_existing_agent(
@@ -523,10 +523,11 @@ defmodule GptAgent do
 
     defp maybe_subscribe(result, _opts), do: result
 
-    defp handle_existing_agent(pid, last_message_id) do
+    defp handle_existing_agent(pid, last_message_id, assistant_id) do
       log("Found existing GPT Agent with PID #{inspect(pid)}")
       log("Updating last message ID to #{inspect(last_message_id)}")
       GenServer.cast(pid, {:set_last_message_id, last_message_id})
+      GenServer.cast(pid, {:set_assistant_id, assistant_id})
       {:ok, pid}
     end
 

mix.exs

@@ -4,7 +4,7 @@ defmodule GptAgent.MixProject do
   def project do
     [
       app: :gpt_agent,
-      version: "6.2.0",
+      version: "7.0.0",
       elixir: "~> 1.16",
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),

test/gpt_agent_test.exs

@@ -281,16 +281,22 @@ defmodule GptAgentTest do
       refute_receive {^pid, %UserMessageAdded{}}
     end
 
-    test "does not update the assistant id on an agent if the agent is already running",
+    test "updates the assistant id on an agent if the agent is already running",
          %{thread_id: thread_id, assistant_id: assistant_id} do
       {:ok, pid1} =
         GptAgent.connect(thread_id: thread_id, last_message_id: nil, assistant_id: assistant_id)
 
+      new_assistant_id = UUID.uuid4()
+
       {:ok, pid2} =
-        GptAgent.connect(thread_id: thread_id, last_message_id: nil, assistant_id: UUID.uuid4())
+        GptAgent.connect(
+          thread_id: thread_id,
+          last_message_id: nil,
+          assistant_id: new_assistant_id
+        )
 
       assert pid1 == pid2
-      assert %GptAgent{assistant_id: ^assistant_id} = :sys.get_state(pid1)
+      assert %GptAgent{assistant_id: ^new_assistant_id} = :sys.get_state(pid1)
     end
 
     test "loads existing thread run status when connecting to thread with a run history", %{