Scaffold hello-world apps, test frameworks, and Gitea CI

- uv workspace tying nisse-core, nisse-dev, nisse-ops together
  (src layouts, workspace-sourced nisse-core dependency)
- Placeholder hello-world entry points for both agents, calling
  through nisse-core to exercise the package boundary
- pytest unit tests per package; integration tests (marker-gated)
  running the installed console scripts as subprocesses
- ruff lint + format, nisse_* declared first-party
- Gitea Actions workflow running lint, format check, unit and
  integration tests; scripts/check.sh mirrors it locally

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nisse-ops/tests/test_ops_main.py

@@ -0,0 +1,10 @@
+import pytest
+
+from nisse_ops.main import main
+
+
+def test_main_prints_greeting(capsys: pytest.CaptureFixture[str]) -> None:
+    main()
+    assert (
+        capsys.readouterr().out == "Hello from nisse-ops, the house spirit is awake.\n"
+    )