

Yes. They can. But they do not mix well with required checks. From githubs own documentation:
If a workflow is skipped due to path filtering, branch filtering or a commit message, then checks associated with that workflow will remain in a “Pending” state. A pull request that requires those checks to be successful will be blocked from merging.
If, however, a job within a workflow is skipped due to a conditional, it will report its status as “Success”. For more information, see Using conditions to control job execution.
So even with github actions you cannot mix a required check and path/branch or any filtering on a workflow as the jobs will hang forever and you will never be able to merge the branch in. You can do either or, but not both at once and for larger complex projects you tend to want to do both. But instead you need complex complex workflows or workflows that always start and instead do internal checks to detect if they need to actually run or not. And this is with github actions - it is worst for external CICD tooling.
Yes magnets can affect HDDs. But it needs to be very strong and close to the HDD. I wouldn’t worry unless you are directly attaching it to you HDD and even then it probably won’t do much if anything at all.
Remember HDDs already have strong permanent magnets inside them. Probably way stronger then the one on the bottom of that support.