Run test coverage on CLI package

[jescalada]

During the Vitest test refactor in #1202, I wasn't able to get CLI test coverage to work correctly, mostly due to problems with the native vitest --coverage command's package resolution. Instead of calculating the coverage % on the CLI files only, it would run the CLI tests and calculate coverage on the entire backend + CLI files. This resulted in abysmal coverage and a failing CI, since it expects to have 80%+ overall coverage.

I experimented with adding a Vitest config file for the CLI only, but I wasn't able to exclude the backend files.

We should figure out the way to calculate coverage for the CLI files correctly and incorporate them to the CI to enforce 80%+ CLI coverage as well.

Additional context
Comment in Vitest refactor PR: #1202 (comment)