Zoekt use repo exists?

What does this MR do and why?

empty_repo? raises an exception when repository does not exist in gitaly. repo_exists? will return false.

AI Summary

This change updates the search indexing logic to be more precise about when to skip repositories. Previously, the code was checking if repositories were "empty" (had no commits), but now it checks if repositories actually "exist" on the file system.

The update affects three areas: task state determination, preflight checks before indexing, and search result handling. In all cases, the logic now focuses on whether the repository physically exists rather than whether it has content. This means that newly created repositories that exist but don't have any commits yet will now be processed for indexing, whereas before they would have been skipped. The comments were also updated to clarify that tasks are marked as complete when repositories don't exist, rather than when they're simply empty.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.