- add philhealth-bst legacy driver fixture
- add PhilhealthBstFixtureTest for host-app YAML validation
- add LegacyPhilhealthBstNormalizerTest scaffold for future normalization
- refactor DriverServiceTest to align with package stubs
- configure test environment for dedicated driver disks
- add DebugTest for Spatie Data config verification

This establishes a clear separation between:
1) package-native driver DSL tests (stubs)
2) legacy host-app driver compatibility (fixtures)

Prepares groundwork for future driver normalization layer.