fix(product-launch): preserve brand font and accent roles

[miguel-heygen]

What

Keep product-launch brand remixing from selecting custom icon fonts as display/body typography and from collapsing a legitimate two-accent palette into one hue.

Why

Two independent product-launch runs required manual frame.md repairs: custom glyph fonts such as vidaXLfont replaced text fonts, while a secondary brand accent used in text/icons was discarded because it had no interactiveBg count.

How

• Centralize and broaden icon-font detection to cover custom *font glyph families.
• Select the secondary accent with the same prominence-aware picker used for the primary, excluding canvas, ink, and the chosen primary.
• Add regression cases for custom icon-font names and a plum/lemon palette where the second accent is not an interactive background.

Test plan

• node --test skills/product-launch-video/scripts/lib/tokens.test.mjs
• bun run test:skills (216 passed)
• bunx oxfmt --check skills/product-launch-video/scripts/build-frame.mjs skills/product-launch-video/scripts/lib/tokens.mjs skills/product-launch-video/scripts/lib/tokens.test.mjs
• bunx oxlint skills/product-launch-video/scripts/build-frame.mjs skills/product-launch-video/scripts/lib/tokens.mjs skills/product-launch-video/scripts/lib/tokens.test.mjs
• bun run lint:skills