This skill should be used when the user says "planning", "arness planning", "plan a feature", "start planning", "I want to build", "new feature", "plan something", "what should I build", "pick an issue", "plan a bug fix", "I have an idea", "spec and plan", "plan from scratch", "plan this", "feature planning", "bug planning", "plan this issue", "arn-planning", or wants to go from an idea, issue, or bug report through to a complete implementation plan ready for execution. Handles severity-aware scope routing across three ceremony tiers (swift, standard, thorough), routing between feature specs, bug specs, and quick implementations, and produces a reviewed plan ready for execution. Chains to arn-implementing at completion.