⁉️ Terminology: clarifying checks, commands and exit codes

The current guidelines on command behavior and return values have led to confusion. We should standardize on terminology around checks, commands, exit codes, success, failure, passing and not passing.

• Today, the check fails if the command's return value is 0.
• We document: This might seem counter-intuitive at first as 0 typically indicates success. The return value of 0 means that the problematic condition was successfully identified.

🥅 Goal + Description of Desired Future State 🌅

The goal of this issue is to discuss inverting the current state and clarifying terminology to reduce confusion moving forward.

• A check is....
• A check includes a command.
• A check can pass or not pass.
• When a check has passed, that means that...
  • the command has ___ and
  • the problematic condition has not been found.
• When a check has not passed, that means that...

✨ Let's update this issue based on what we discuss.

🐾 Next Steps

Based on the decision we make here, we might need to rewrite the checks. If we do need to do that, let's make sure we include all applicable changes in that effort. (See this comment on line folding.)

• Test that negation in playbook generation works as expected in branch mg-verify-negation-20250515
• Create negation branch
• Update docs -> merge into negation branch
• Work with check authors to invert checks
• + Maintainers 🧪 test

🥅 Goal: make this go without breaking GitLab Detective in the interim.