Refactor pkgmgr into modular installer pipeline with Nix flake support, PKGBUILD build workflow, local Nix cache, and full test suite restructuring.

See conversation: https://chatgpt.com/share/69332519-7ff4-800f-bc21-7fcd24a66c10

tests/integration/deactivated_test_integration_install_all_shallow.py

@@ -0,0 +1,46 @@
+"""
+Integration test: install all configured repositories using
+--clone-mode shallow (HTTPS shallow clone) and --no-verification.
+
+This test is intended to be run inside the Docker container where:
+  - network access is available,
+  - the config/config.yaml is present,
+  - and it is safe to perform real git operations.
+
+It passes if the command completes without raising an exception.
+"""
+
+import runpy
+import sys
+import unittest
+
+
+class TestIntegrationInstallAllShallow(unittest.TestCase):
+    def test_install_all_repositories_shallow(self):
+        """
+        Run: pkgmgr install --all --clone-mode shallow --no-verification
+
+        This will perform real installations/clones inside the container.
+        The test succeeds if no exception is raised.
+        """
+        original_argv = sys.argv
+        try:
+            sys.argv = [
+                "pkgmgr",
+                "install",
+                "--all",
+                "--clone-mode",
+                "shallow",
+                "--no-verification",
+            ]
+
+            # Execute main.py as if it was called from CLI.
+            # This will run the full install pipeline inside the container.
+            runpy.run_module("main", run_name="__main__")
+
+        finally:
+            sys.argv = original_argv
+
+
+if __name__ == "__main__":
+    unittest.main()