Make models selectable

test/controllers/admin/prompt_sandboxes_controller_test.rb

@@ -14,7 +14,8 @@ class Admin::PromptSandboxesControllerTest < ActionDispatch::IntegrationTest
   test "create processes prompt and renders show with summary" do
     post admin_prompt_sandbox_path, params: { prompt: "Test prompt for summarization" }
 
-    assert_response :success
+    assert_response :redirect
+    assert_redirected_to admin_prompt_sandbox_path(day: assigns(:day_timeline).day, llm_model: Event::Summarizer::LLM_MODEL)
   end
 
   test "non-staff user gets forbidden on show" do