tests/__init__.py keeps a run offline, its scratch under tmp/ and its
installer cache its own, but only discover -s tests -t . imported it.
discover tests ran with RETROBIOS_OFFLINE unset, scratch on the /tmp
tmpfs and the user's real installer cache, the setting in which e2e
fixtures had written into the shared .cache/large. Every test module now
imports the package first, and a test fails on a module that does not.
test_verify_listing.py took its line with the previous commit.
game_dat_importer and arcade_parent_importer each kept an exact-text
copy of write_if_changed, so a redump refresh rewrote every catalog for
its fetched date alone. Both now use artifacts.write_if_changed, which
treats fetched as a timestamp. A No-Intro rebuild still rewrites its
catalogs, since asset_updated_at moves with it, so check_freshness keeps
reading a fetched date no older than the pack.
Abdessamad Derraz