fix(chopper): expire unused attic objects after 90 days

[devusb]

garbage-collection.interval was set to 14 days, but default-retention-period was never set. It defaults to Duration::ZERO, which disables time-based collection entirely — so the collector has been waking up every two weeks and deleting nothing, and the cache has been retaining everything since it was stood up.

This sets a 90 day default retention. Objects become eligible only when both created_at and last_accessed_at are older than the cutoff, so anything actively pulled keeps resetting its own clock.

Note for caches that must never expire

Attic excludes any cache whose effective retention is 0 from time-based GC (the GC query filters on retention_period.ne(0), falling back to the global default when the per-cache value is NULL). To pin one:

attic cache configure <cache> --retention-period "0s"

Watch out when reconfiguring such a cache later — attic cache configure resets retention_period to the global default whenever --retention-period is not passed, so pass it on every configure call for that cache.

Verification

• nix eval .#nixosConfigurations.chopper.config.containers.attic.config.services.atticd.settings.garbage-collection → {"default-retention-period":"90 days","interval":"14 days"}
• nix fmt reports 0 changed files

Not yet deployed — this only changes the config.

https://claude.ai/code/session_01TMTHV4JBQMmtSLPoRkbZie