Claude Code sessions erase after 30 days by default

I've been using Claude Code heavily since January. I recently used the `ccusage` utility to measure my usage and noticed a drop after 30 days. It turns out that, by default, Claude Code erases your sessions after 30 days. You can fix this by bumping `cleanupPeriodDays` to a big number like 999999999 in your `config.json`.