Proposal : have the specs save in a specific directory structure

Hi,
Thanks for sharing this is very helpful.

Now in my use I saw when I started from /spec step it just created SPEC.md in root of the project, so when it's time for next feature it overrites existing one. So I was thinking if we create maybe feature wise directories `/docs/features/feature-X/spec.md ` then it might be better. Also we could have maybe claude session written somewhere with feature so that multiple simultinious work is easier.

Thanks