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

pyproject.toml

@@ -50,14 +50,14 @@ Repository = "https://github.com/spalencsar/bearhub"
 license-files = ["LICENSE"]
 
 [tool.setuptools.dynamic]
-version = {attr = "bauh.__version__"}
+version = {attr = "bearhub.__version__"}
 
 [tool.setuptools.packages.find]
 exclude = ["tests.*", "tests"]
 
 [tool.setuptools.package-data]
-bearhub = ["desktop/*"]
-bauh = [
+bearhub = [
+    "desktop/*",
     "view/resources/locale/*",
     "view/resources/img/*",
     "view/resources/style/*",
@@ -65,3 +65,4 @@ bauh = [
     "gems/*/resources/img/*",
     "gems/*/resources/locale/*",
 ]
+bauh = []