Refreshes .claude/skills/ from upstream stacksjs/stacks (storage/framework/defaults/ai/skills, main).
Why: these skills are committed project files seeded at scaffold time; the @stacksjs/skills package only reads them, and buddy upgrade vendors core/* (not defaults/), so nothing was syncing them — they'd drifted behind upstream.
What changed: 93 → 105 skills. 48 files added, 40 updated.
New (12, all design-focused — handy for the in-flight Crosswind/design work):
stacks-brandkit · stacks-design-taste · stacks-design-taste-codex · stacks-design-brutalist · stacks-design-minimalist · stacks-design-soft · stacks-design-output · stacks-redesign · stacks-image-to-code · stacks-imagegen-web · stacks-imagegen-mobile · stacks-technical-diagrams
Already usable in the working tree; this PR is just the repo record. (Unrelated config/crosswind.ts WIP is intentionally not included.)