fix(site): reduce marketing site to editorial core

[drewstone]

What changed

This reduces the public marketing site to the surfaces we want to keep right now:

• keeps the purple homepage hero and removes the rejected below-fold marketing sections
• removes weak product, protocol, legal, preview, status, and service routes from the live page tree
• simplifies the nav and footer to Home, Blog, Research, Docs, Launch, and Follow
• adds a light editorial Research page for the self-improving agent series
• simplifies the Blog index into a light editorial index instead of series/card taxonomy blocks
• repairs blog links that pointed at deleted service pages by sending them to active Tangle GitHub repos

Why

The previous site was showing too many weak surfaces at once. This PR narrows the public site to the hero, blog, and research until product pages have real artifacts worth publishing.

Validation

• git merge-tree --write-tree origin/master HEAD
• pnpm build
• Playwright smoke pass for /, /blog, and /research on desktop and mobile
• Checked visible nav/footer links do not point to deleted routes
• Checked deleted routes are absent from the generated sitemap

[tangletools]

✅ Auto-approved drewstone PR — ea4591e0

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

_{tangletools · auto-approval · reason: drewstone_author · 2026-07-01T17:02:54Z}