Add automated tests for bootstrap core and adapters #20

Summary

Add automated test coverage for the bootstrap foundation so core behaviour, detection, execution, CLI handling, configuration, and distro adapters can evolve safely.

Scope

• Add tests for distribution detection using controlled os-release fixtures
• Test architecture normalization
• Test supported and unsupported distro selection
• Test command-line argument parsing and validation
• Test dry-run command execution
• Test privileged execution behaviour without modifying the host
• Test distribution adapter loading and contract validation
• Establish a repeatable local test command

Acceptance Criteria

• Tests do not modify the developer workstation
• Distribution detection tests use fixtures or controlled overrides where appropriate
• Architecture normalization is covered
• Valid and invalid CLI arguments are covered
• Dry-run behaviour is verified
• Privileged execution can be tested without performing privileged system changes
• Missing or incomplete distro adapters are covered
• Tests return reliable pass/fail exit codes
• The test suite can be executed locally using a documented command