Initialize product requirements document

Initialize PRD and link progress ledger for structured ralph-loop execution

When you need a structured Product Requirements Document with testable acceptance criteria before running ralph-loop iteration.

• · project or feature description string

• · .omx/plans/prd-{slug}.md (PRD)
• · .omx/state/{scope}/ralph-progress.json (ledger)

• · working directory has .omx/ or it will be created

• · PRD slug collision (overwrites existing PRD)
• · Progress ledger not synced with PRD (legacy .omx/prd.json not auto-migrated)

• · PRD schema includes problem, goals, non-goals, acceptance criteria, constraints
• · Links canonical source (markdown) for long-term reference