[FEATURE] Ability to set session summary from within the session

I have tons of sessions, often for the same branch and at the same time etc and it's really painful for me to find the right one to resume as what -r is giving is auto-generated and (worse) artificially truncated to 60 chars or so. I'd love to be able to override the auto-generated session summary (say with /summary <WHATEVER> (with no length limit for <WHATEVER>) ) that then should stay immutable. While I do not seem much use case that myself, the /summary should most likely be accompanied by counter command to revert back to auto generated summary (i.e. /auto-summary).