feat: add create-project command

[vildanbina]

Summary

• Adds /yavy:create-project command to the Claude Code plugin
• Interactive flow: choose source type (URL or GitHub), collect source, resolve org, optional settings
• Delegates to yavy project create CLI command (added in feat: add yavy project create command cli#3)
• Offers to run yavy init after creation to immediately set up the skill

Test plan

• Run /yavy:create-project with a web crawl URL
• Run /yavy:create-project with a GitHub repo
• Verify it handles missing CLI / unauthenticated state gracefully
• Verify org auto-selection with single org account
• Verify org prompt with multi-org account