feat(site): home page fixes from the design review #5

Summary

Moving CryptOS-PKI/docs#118 here: the home page it was filed against is now this site, not
the docs site, now that the product-site decision landed. I seeded the real site in
#3 from the approved proof, which covers some of these items already. I'm
listing all nine here with their current status so the ones still open don't get lost.

Acceptance criteria

• Hero: a split hero -- eyebrow, a two-line headline with the second line in the accent
  colour, a lede with key terms highlighted, a primary and a secondary button, a terminal-style
  card on the right, over a faint grid backdrop with a soft blurred glow top-right. Done in the
  seeded site (SplitHero/TerminalCard).
• Trademark notices (the (tm) marks). Done in the seeded site's footer.
• Use the CryptOS and FleetOS marks (horizontal/stacked lockups, light/dark, SVG) from the
  design set. Done via the vendored @cryptos-pki/ui kit's Wordmark/FleetosMark.
• Colour: the section boxes were too dark against the background on the docs-site home page.
  The seeded site is a new design, not a copy of that page, so I want this re-checked against the
  new design rather than assumed fixed.
• The warning: black text on orange can't be read from a distance; needs an accessible pair
  (WCAG AA contrast) and a link to the page that explains it. The seeded site carries no pre-1.0
  warning banner yet -- this still needs doing, on the new design.
• Remove the mid-page "Pre-1.0" line, or make it the real warning. Same as above: the seeded
  site has no such line yet, so this folds into the warning item above once a banner exists.
• Add the PKI RFCs / CA/Browser Forum Baseline Requirements / "your own IANA Private
  Enterprise Number" claim, linking to /docs/using/tsa-policy-oid, checked against that page and
  the code before publishing. Not yet in the seeded content; needs the same fact-check the
  original issue called for.
• The emoji treatment on headings, in my README style. A design call for the new site, not
  carried over automatically -- the seeded site's headings don't use it yet.
• The footer's project links wrapping too early. The seeded site has a different footer than
  the one this was filed against; re-check whether the new layout has the same problem.

Notes

From the docs-site design review on 2026-10-15, originally CryptOS-PKI/docs#118.