feat(harness): config.py + workspace.py (D3 confine) + chirone.example.yaml

- config.py ported from ChironeWp3, PSD_PROFILE -> THOTH_PROFILE; dual vector key
  (vector_rest/vector_write_rest top-level) preserved verbatim
- workspace.py: thin boundary wrapper (D3) around load_config
- workspaces/chirone.example.yaml: aligned to the real Config shape
- tests/test_workspace.py: 2 tests (env expand + dual key; missing env raises)
- .env.example: added DWH + DOCS_ROOT vars
All tests pass (2/2).

harness/tests/conftest.py

@@ -0,0 +1,12 @@
+import os
+import sys
+from pathlib import Path
+
+# Permetti `pytest` lanciato da qualsiasi directory di trovare il package `nsp`
+# (installato in modalità editable nella venv, ma utile anche senza attivazione).
+_ROOT = Path(__file__).resolve().parent.parent
+if str(_ROOT) not in sys.path:
+    sys.path.insert(0, str(_ROOT))
+
+# Directory sessions/ risolta relativamente alla root harness (per i test che creano sessioni)
+os.environ.setdefault("NSP_HARNESS_ROOT", str(_ROOT))