Fix skill description to single-line format for correct parsing

Add marketplace.json for direct plugin installation

Remove webpage and consulting-output from public repo; tighten gitignore

Remove duplicate root SKILL.md — canonical location is skills/modelling-team/SKILL.md

Complete skill update: challenger subtotal check, sync all reference files

Add subtotal and assumption decomposition rules; add plugin structure

Sharpen landing page positioning for ads test

Add webpage (index.html v1), gitignore, and validation strategy notes

Initial release: three-agent Excel modelling skill for Claude Code

Initial commit