docs: organize Python helpers and refresh README (#334)

* docs: organize Python helpers and refresh README

* docs: add README status badges

* test: centralize Python helper test imports

* docs: add short provenance disclaimer

python/tests/conftest.py

@@ -0,0 +1,5 @@
+from pathlib import Path
+import sys
+
+# Make the sibling `python/` helper modules importable from this test package.
+sys.path.insert(0, str(Path(__file__).resolve().parents[1]))