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/web/test_controller.py

@@ -1,10 +1,10 @@
 from unittest import TestCase
 from unittest.mock import Mock, patch
 
-from bauh.gems.web.controller import DEFAULT_LANGUAGE_HEADER
-from bauh.gems.web.controller import WebApplicationManager
+from bearhub.gems.web.controller import DEFAULT_LANGUAGE_HEADER
+from bearhub.gems.web.controller import WebApplicationManager
 
-LOCALE_TARGET = 'bauh.gems.web.controller.locale.getlocale'
+LOCALE_TARGET = 'bearhub.gems.web.controller.locale.getlocale'
 
 
 class ControllerTest(TestCase):

tests/gems/web/test_namespace.py

@@ -0,0 +1,22 @@
+from unittest import TestCase
+
+from bearhub.gems.web.controller import WebApplicationManager
+from bearhub.view.core.gems import _discover_gem_dirs, _import_controller_module
+
+
+class TestWebNamespace(TestCase):
+
+    def test_bauh_compat_import(self):
+        from bauh.gems.web.controller import DEFAULT_LANGUAGE_HEADER
+
+        self.assertEqual('en-US, en', DEFAULT_LANGUAGE_HEADER)
+
+    def test_web_discovered_under_bearhub(self):
+        gem_dirs = dict(_discover_gem_dirs())
+        self.assertIn('web', gem_dirs)
+        self.assertIn('bearhub/gems/web', gem_dirs['web'].replace('\\', '/'))
+
+    def test_controller_import_prefers_bearhub(self):
+        module = _import_controller_module('web')
+        self.assertEqual(module.__name__, 'bearhub.gems.web.controller')
+        self.assertIs(module.WebApplicationManager, WebApplicationManager)