Developed and tested on Zen, primarily for Zen. Minimal extension to match what Arc browser offers natively: closing inactive tabs after a given delay (defaults to 7 days, configurable 1-365). Closed tabs are still visible as part of History / Recently closed tabs. First run, open the extension's property to set your auto-close delay, save and that's it. By default, a tab close check happens every hour (you can configure it).
