Match upstream-error test to sanitized client messages

Core 7603cf7 (in v0.2.5) keeps transport failure detail out of client
messages: the SSE error event now carries a generic upstream_error, and
the status/body detail rides the Failed outcome to operator logs. The
test asserted the old leaky behavior, which only survived this long
because the lock pinned a pre-rebase observer-port commit that predated
the change.

Author: BinaryMuse

test/atuin_ai_server_test.exs

@@ -169,7 +169,7 @@ defmodule AtuinAI.ServerTest do
     assert Plug.Conn.get_req_header(upstream_conn, "authorization") == []
   end
 
-  test "an upstream HTTP error fails the turn fast with the status and body", %{
+  test "an upstream HTTP error fails the turn fast with a generic error event", %{
     server_port: port
   } do
     body =
@@ -193,8 +193,14 @@ defmodule AtuinAI.ServerTest do
     {:ok, {{_, 200, _}, _headers, response}} = Task.await(task, 5000)
     response = to_string(response)
 
-    assert response =~ "HTTP 404"
-    assert response =~ "not found, try pulling it first"
+    assert response =~ "event: error"
+    assert response =~ ~s("code":"upstream_error")
+    assert response =~ "LLM request failed, please retry"
+
+    # Since core v0.2.5 the upstream status and body are operator detail
+    # (logged via the Failed outcome); they must not reach the client.
+    refute response =~ "HTTP 404"
+    refute response =~ "not found, try pulling it first"
   end
 
   test "unknown model alias is a 400", %{server_port: port} do