feat(content-cards): add air theme and chart layouts

[Wandi-Liao]

What changed

• Added the transparent air theme with a bundled Lexend font.
• Added metric, comparison, and chart layouts with structured data validation and updated review examples.

Files changed

M skills/video-add-content-cards/SKILL.md
M skills/video-add-content-cards/assets/content-cards-review.html
A skills/video-add-content-cards/assets/fonts/Lexend-VariableFont_wght.ttf
M skills/video-add-content-cards/examples/build-gallery.mjs
M skills/video-add-content-cards/examples/gallery-animated.html
A skills/video-add-content-cards/examples/index-air.html
M skills/video-add-content-cards/examples/index-almanac.html
M skills/video-add-content-cards/examples/index-apex.html
M skills/video-add-content-cards/examples/index-dotgrid.html
M skills/video-add-content-cards/examples/index-editorial.html
M skills/video-add-content-cards/examples/index-teal.html
M skills/video-add-content-cards/examples/shoot.mjs
A skills/video-add-content-cards/reference/chart-data.md
M skills/video-add-content-cards/reference/ux-design.md
M skills/video-add-content-cards/scripts/apply_cards_review.py
M skills/video-add-content-cards/scripts/build_cards_plan.py
M skills/video-add-content-cards/scripts/build_review_page.py

Why it changed

Content cards need more evidence-backed visual treatments without weakening plan, review, clearance, or deterministic-rendering contracts.