feat: Phase 2 (fragment migration), Phase 3 (testing infrastructure), Phase 4 (CI/CD)

Phase 2: Fragment Migration
- Migrated 42 ingredients to 54 fine-grained fragments
- Replaced %include with %ksappend syntax
- Created organized fragment structure (platform/generic-43, platform/generic-rawhide, shared/)
- Updated generator to use fragment paths
- All 16 manifest variants generate successfully

Phase 3: Testing Infrastructure
- Created containerized test runner (tests/container/)
- Added integration test suite (tests/integration/)
- Created golden master fixtures (tests/fixtures/expected_recipes/)
- 41 tests passing (36 unit + 5 integration)
- 54 fragments, 16 recipes validated

Phase 4: CI/CD Integration
- 5 new workflows: validate-recipes, validate-fragments, test-generation, container-tests, build-iso
- Added validation gates before ISO builds
- Works with existing fedora-runner-image
- Local testing support via act_runner

fragments/shared/desktop/labwc/config.ks

@@ -0,0 +1,19 @@
+# Untested
+
+xconfig --startxonboot # Start the display session on boot. Although it says --startx, which seems to imply xorg, it is actually generic and thus works also with Wayland.
+
+%packages --exclude-weakdeps # Beginning of the packages section. Excludes weak package dependencies.
+
+@base-graphical
+## provides the following as mandatory packages:
+# mesa-dri-drivers
+# mesa-vulkan-drivers
+# plymouth-system-theme
+
+labwc # A Wayland window-stacking compositor
+
+## Extra hand-picked packages
+firefox # Mozilla Firefox Web browser
+mozilla-ublock-origin.noarch # An efficient blocker for Firefox
+
+%end # End of the packagages section