docs: align benchmark guide and templates with real adapter API

tests/test_env_template.py

@@ -0,0 +1,13 @@
+from skillopt.datasets.base import SplitDataLoader
+from skillopt.envs._template.env_template import TemplateBenchmarkAdapter
+from skillopt.envs._template.loader_template import TemplateBenchmarkDataLoader
+
+
+def test_template_adapter_is_concrete():
+    adapter = TemplateBenchmarkAdapter()
+    assert adapter.get_task_types() == ["your_benchmark"]
+
+
+def test_template_loader_uses_split_dataloader():
+    loader = TemplateBenchmarkDataLoader()
+    assert isinstance(loader, SplitDataLoader)