refactor(models): unify preset names

tests/agent/test_model_runtime_resolver.py

@@ -361,3 +361,15 @@ def test_resolver_mutates_only_its_default_selection() -> None:
     assert resolver.model_preset is None
     assert initial.model == "base-model"
     assert initial.context_window_tokens == 10_000
+
+
+def test_resolver_preserves_canonical_preset_name_for_case_insensitive_input() -> None:
+    resolver = ModelRuntimeResolver(
+        _runtime(),
+        model_presets={"Deep Research": ModelPresetConfig(model="deep-model")},
+    )
+
+    selected = resolver.select_preset("deep research")
+
+    assert selected.model == "deep-model"
+    assert selected.model_preset == "Deep Research"