Add X-Squad educational output style for Claude Code

[strickvl]

Summary

• Adds a custom Claude Code output style (zenml-x-team) designed for backend developers working on frontend repos
• Provides brief educational "Insight" boxes explaining frontend patterns and how CLAUDE.md conventions influence implementation choices
• Fixes .gitignore to properly allow .claude/output-styles/ while ignoring other .claude/ contents

Usage

/output-style zenml-x-team

Test plan

• Clone repo and run /output-style zenml-x-team in Claude Code
• Verify insights appear when working on frontend tasks
• Confirm the style is portable (references project CLAUDE.md, not hardcoded paths)