* docs: add skeleton for "Data Designer Got Skills" dev note
* create assets folder and add blog directory name
* docs: add Claude Code plugin marketplace configuration
Register the repo as a Claude Code plugin marketplace so users can
install the data-designer skill via `/plugin marketplace add`.
* docs: write first draft of "Data Designer Got Skills" dev note
Full prose for all sections: intro with hero benchmark figure,
agents as first-class users, baseline trace walkthrough, CLI and
skill design, benchmark results (228 sessions), getting started
with marketplace and npx install paths, and what's next.
* docs: add error breakdown table and minor refinements
* docs: add sdg and data-designer keywords to plugin metadata
* docs: refine CLI framing, reduce em dashes, slop guard pass
* docs: fix grammar in dev note (serial comma, double-which clause)
* update hero image
* docs: swap hero image, move benchmark figure, minor wording tweaks
* docs: add narrative lead-in to skill trace summary
* docs: refine quality bullet, streamline getting started modes
* remove old image
* slope-guard tweaks
