feat: add gpt-6.1-terra and default exploration to high reasoning

tests/unit/admin_console/test_model_settings.py

@@ -96,6 +96,7 @@ def test_model_presets_keep_supported_choices_without_restricting_custom_names()
     presets = service.get_model_settings()["model_presets"]
     assert presets == [
         "gpt-6-luna",
+        "gpt-6.1-terra",
         "gpt-6.1-sol",
         "gpt-6-astra",
         "mimo-v2.6-pro",