Skills from snarktank/ralph

Generate a Product Requirements Document (PRD) for a new feature. Use when planning a feature, starting a new project, or when asked to create a PRD. Triggers on: create a prd, write prd for, plan this feature, requirements for, spec out.

Converts PRDs into Ralph's `prd.json` format, writing `prd.json` in the ralph directory and managing `progress.txt` and `archive/YYYY-MM-DD-feature-name/`; it also references `ralph.sh` and the `dev-browser skill` for automation/verification. No security-relevant behaviors detected.