The issue turned out to be that the pandas repository's settings were
pointed to a CI settings file outside the repository, so it wasn't even
looking at my debian/salsa-ci.yml.
As suggested by Eriberto's link, this setting is found at (starting from
the repository's page in Salsa, logged in) Settings (in left menubar) >
CI/CD > General pipelines > Expand > CI/CD configuration file.
After pointing that setting back at debian/salsa-ci.yml, it does take
the absence of such a file as "do nothing".
The timeout length setting is on the same page.
