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/platform/generic-rawhide/bootloader/grub.ks

@@ -0,0 +1,3 @@
+# GRUB bootloader configuration for live media (no location, minimal timeout)
+
+bootsupport --timeout=1 # Set the GNU GRUB bootloader timeout to 1 and to location to none

fragments/platform/generic-rawhide/bootloader/systemd-boot.ks

@@ -0,0 +1,3 @@
+# systemd-boot bootloader configuration for live media (no location, minimal timeout)
+
+bootsupport --sdboot --location=none --timeout=1 # Use systemd-boot and set location to none