The config's files list still referenced the README's placeholder
filenames (playlist1.m3u, playlist2.m3u), which don't exist in this
repo, so the linter was silently checking nothing. Point it at the
real playlist.m3u8, drop the noisy full-file cat dump, and surface
its output in the job summary like the iptv-checker step.
Add a job summary listing the failed channels and upload the full
online.m3u/failed.m3u results as a build artifact, instead of running
the checker and discarding its output.