[Feature Request] Add config option for time-based retention of failed commands

I want to keep failed commands temporarily so I can review recent errors, but I don't want them cluttering my history forever. Currently store_failed is all-or-nothing: true stores them permanently, false discards them immediately. There's no way to say "keep failures for a short window, then auto-delete."

A config option like: store_failed = true failed_retention = "5m" # or 1h, 1d, etc. Or a separate timer: store_failed_retention_duration.