feat(cli): add open-reuse validate and register portfolio integrations

Implement Integration Definition validator CLI with schema and index checks,
pytest suite, and CI workflow. Register open-cmis-tck and issue-core-gitea in
the integration index.

Closes OPEN-WP-0003 and OPEN-WP-0004.

open_reuse/__init__.py

@@ -0,0 +1,3 @@
+"""open-reuse integration registry tooling."""
+
+__version__ = "0.1.0"