M3 namespace migration: complete Phase B, partial Phase D, docs and tests

- Native runtime under bearhub/ (api, commons, gems, view/util, view/core, view/qt)
- bauh/ compatibility re-export shims for legacy imports
- Phase D: canonical __version__/__app_name__ in bearhub/__init__.py; pyproject.toml
  and setup.py point at bearhub package
- Native gem loader at bearhub/view/core/gems.py
- Namespace compatibility tests (159 tests passing)
- Documentation: CHANGELOG [Unreleased], NAMESPACE_MIGRATION, ROADMAP, README,
  CONTRIBUTING, docs/qt6-migration.md, packaging/aur/README.md

tests/gems/flatpak/test_controller.py

@@ -1,8 +1,8 @@
 from unittest import TestCase
 from unittest.mock import Mock
 
-from bauh.gems.flatpak.controller import FlatpakManager
-from bauh.gems.flatpak.model import FlatpakApplication
+from bearhub.gems.flatpak.controller import FlatpakManager
+from bearhub.gems.flatpak.model import FlatpakApplication
 
 
 class FlatpakManagerSortUpdateOrderTest(TestCase):

tests/gems/flatpak/test_flatpak.py

@@ -2,13 +2,13 @@ from unittest import TestCase
 from unittest.mock import patch, Mock
 
 
-from bauh.gems.flatpak import flatpak, VERSION_1_2
+from bearhub.gems.flatpak import flatpak, VERSION_1_2
 
 
 class FlatpakTest(TestCase):
 
-    @patch("bauh.gems.flatpak.flatpak.SimpleProcess")
-    @patch("bauh.gems.flatpak.flatpak.ProcessHandler.handle_simple", return_value=(True, """
+    @patch("bearhub.gems.flatpak.flatpak.SimpleProcess")
+    @patch("bearhub.gems.flatpak.flatpak.ProcessHandler.handle_simple", return_value=(True, """
     Looking for updates...
 
     \tID\tArch\tBranch\tRemote\tDownload

tests/gems/flatpak/test_namespace.py

@@ -0,0 +1,22 @@
+from unittest import TestCase
+
+from bearhub.gems.flatpak.controller import FlatpakManager
+from bearhub.view.core.gems import _discover_gem_dirs, _import_controller_module
+
+
+class TestFlatpakNamespace(TestCase):
+
+    def test_bauh_compat_import(self):
+        from bauh.gems.flatpak.model import FlatpakApplication
+
+        self.assertTrue(issubclass(FlatpakApplication, object))
+
+    def test_flatpak_discovered_under_bearhub(self):
+        gem_dirs = dict(_discover_gem_dirs())
+        self.assertIn('flatpak', gem_dirs)
+        self.assertIn('bearhub/gems/flatpak', gem_dirs['flatpak'].replace('\\', '/'))
+
+    def test_controller_import_prefers_bearhub(self):
+        module = _import_controller_module('flatpak')
+        self.assertEqual(module.__name__, 'bearhub.gems.flatpak.controller')
+        self.assertIs(module.FlatpakManager, FlatpakManager)

tests/gems/flatpak/test_worker.py

@@ -1,6 +1,6 @@
 from unittest import TestCase
 
-from bauh.gems.flatpak.worker import FlatpakAsyncDataLoader
+from bearhub.gems.flatpak.worker import FlatpakAsyncDataLoader
 
 
 class FlatpakAsyncDataLoaderTest(TestCase):