Summary

I grouped two very small fixes to the CLI into this since I didn't want to open a PR for each of these:

• The first change is to use checked arithmetic when calculating the number of processed files. The CLI checks that at least one file was processed by subtracting the number of skipped files from the total number of files that were read, however in case a file fails to be read from the disk it will increment the skipped counter but not the total counter, making the subtraction panic in debug builds and to an integer underflow on release builds.
• The second change is an update to the Unix-specific snapshots of the CLI that were missed when I merged fix(rome_cli): normalize the content of CLI snapshots #3835, since I ran the snapshot update on Windows but not on Unix.

Test Plan

I've added a new test case for the first change, and the second one is specifically about fixing tests anyway.