feat: add python source loader

tests/wf_sources_python/test_loader.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import pytest
+
+from wf_sources_python import load_python_source
+
+
+def test_load_python_source_from_sequence_registry() -> None:
+    source = load_python_source(
+        source_id="local.ops",
+        module="tests.fixtures.python_source_ops",
+        registry="registry",
+    )
+
+    assert source.id == "local.ops"
+    assert source.kind == "python"
+    assert set(source.capabilities.node_specs) == {
+        "local.ops.echo",
+        "local.ops.upper",
+    }
+    assert source.permissions.safe_for_workflow is True
+
+
+def test_load_python_source_rejects_missing_registry() -> None:
+    with pytest.raises(ValueError, match="missing registry object"):
+        load_python_source(
+            source_id="local.ops",
+            module="tests.fixtures.python_source_ops",
+            registry="missing",
+        )
+
+
+def test_load_python_source_rejects_non_node_spec() -> None:
+    with pytest.raises(TypeError, match="expected NodeSpec"):
+        load_python_source(
+            source_id="local.ops",
+            module="math",
+            registry="pi",
+        )