- Send log messages to stderr in find_working_repo() to avoid
polluting the URL output captured by configure_repo()
- Actually download and validate Packages.gz file content instead
of just checking if server responds (spider check)
- Handle find_working_repo() failure gracefully with || true
- Clean up old feed entries properly when reconfiguring
Fixes the issue where log messages were being written to
customfeeds.conf along with the URL.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>