feat: return structured clone commands from git adapters

[TorstenDittmann]

Summary

• replace generateCloneCommand() string assembly with Utopia\Command composition across the shared adapter contract and the GitHub, Gitea, and GitLab adapters
• remove shell-only clone steps by switching to git -C, git sparse-checkout set --no-cone, and PHP-side GitHub wildcard tag resolution
• update clone tests to assert Command instances and execute them through Console::execute(...)

Testing

• composer lint
• composer check
• composer test (fails in this environment because the GitHub app key and Gitea/Gogs access token test credentials are not configured)