Full Testing harness

[OliverRC]

Up till now I relied on the work being hand tested. I want this automated.

I want tests that ensure the tools behaviour is perfect.

It must test the:

• different modes.
• dry run does not make changes
• different comands

We may need to simulate GIT, GitHub, FTP to end-to-end test the app.

Should have integration tests as well as unit tests.

[OliverRC]

Completed by Sandcastle in PR #11.

Added a full automated testing harness (46 tests):

• Unit tests for all services, using real temporary git repositories to prove the Tags/GitHubMergePR find modes end-to-end.
• Integration tests that drive the compiled CLI as an external process, covering command wiring, argument validation, all three deployment modes (Tags, GitHubMergePR, Folder), and verifying that a dry run reports planned changes without connecting to the remote server or modifying local files.

Note: the CI token lacks 'workflow' scope so the 'dotnet test' step could not be added to the GitHub Actions workflow automatically — a maintainer should add it. Live SFTP/FTP end-to-end testing (containerised server) was deferred as dry-run covers the safety path.