fix: implement TD-08, remove test sandbox scaffolding from production code

test/bds/ai/chat_sandbox_cleanup_test.exs

@@ -0,0 +1,65 @@
+defmodule BDS.AI.ChatSandboxCleanupTest do
+  use ExUnit.Case, async: false
+
+  alias BDS.AI
+  alias BDS.Repo
+
+  defmodule FakeSecretBackend do
+    def encrypt(value), do: {:ok, "enc:" <> value}
+
+    def decrypt("enc:" <> value), do: {:ok, value}
+    def decrypt(_other), do: {:error, :invalid_ciphertext}
+  end
+
+  defmodule FinalReplyRuntime do
+    def generate(endpoint, request, opts) do
+      send(Keyword.fetch!(opts, :test_pid), {:runtime_request, endpoint, request})
+      {:ok, %{content: "All set.", usage: %{input_tokens: 5, output_tokens: 2}}}
+    end
+  end
+
+  setup do
+    :ok = Ecto.Adapters.SQL.Sandbox.checkout(BDS.Repo)
+    :ok
+  end
+
+  test "chat module does not carry SQL sandbox scaffolding" do
+    source_path = Path.expand("../../../lib/bds/ai/chat.ex", __DIR__)
+    source = File.read!(source_path)
+
+    refute source =~ "sandbox_ready"
+    refute source =~ "allow_repo_sandbox"
+    refute source =~ "Ecto.Adapters.SQL.Sandbox"
+  end
+
+  test "send_chat_message persists through the supervised task without explicit sandbox allowance" do
+    assert {:ok, _endpoint} =
+             AI.put_endpoint(
+               :online,
+               %{
+                 url: "https://api.example.test/v1",
+                 api_key: "online-secret",
+                 model: "gpt-4o-mini"
+               },
+               secret_backend: FakeSecretBackend
+             )
+
+    assert :ok = AI.set_airplane_mode(false)
+    assert {:ok, conversation} = AI.start_chat(%{title: "Sandbox Cleanup", model: "gpt-4o-mini"})
+
+    assert {:ok, reply} =
+             AI.send_chat_message(conversation.id, "How many items are in the blog?",
+               runtime: FinalReplyRuntime,
+               test_pid: self(),
+               secret_backend: FakeSecretBackend
+             )
+
+    assert reply.assistant_message.content == "All set."
+
+    messages = AI.list_chat_messages(conversation.id)
+    assert Enum.map(messages, & &1.role) == [:user, :assistant]
+
+    assert Repo.aggregate(BDS.AI.ChatMessage, :count, :id) == 2
+    assert_received {:runtime_request, _endpoint, %{operation: :chat}}
+  end
+end