feat(web): permissions docs + landing revamp

[karngyan]

Summary

Website catch-up for the per-site permission tiers shipped in extension v0.3.0 (#15), plus a landing page revamp.

Permissions content

• New /docs/permissions page: tiers (deny / read / full), both-ends navigation check, wildcard matching precedence, popup-only grant path, CLI examples, the policy_denied error agents see
• Commands page: new "Site permissions" group (reins policy, deny, readonly, allow-always-errors)
• Security page: "Per-site permissions" section; stored-state bullet now mentions the policy
• Privacy page: policy storage disclosed, "Last updated" bumped

Landing revamp

• Hero terminal types itself out (char-by-char prompts, blinking caret; instant under prefers-reduced-motion; ghost transcript prevents layout shift)
• "Unlimited ideas" section: 6 use-case chips, each auto-playing a real command sequence in a terminal, cycling with click-to-jump
• "You hold the reins" trust section: tier copy + HTML mock of the extension popup whose Full/Read/Deny control animates to Deny on scroll-in
• Scroll-reveal animations (IntersectionObserver + CSS, no new dependency)
• Sticky glass navbar: Docs / Commands / Permissions links, GitHub icon, Get started CTA; docs sidebar offset adjusted to match
• Gradient hairline dividers between all landing sections

Test plan

• pnpm typecheck, biome check, pnpm build (prerenders all 11 pages incl. /docs/permissions) — all green
• Served dist locally and manually verified docs pages render (table, code blocks, links)
• Landing animations verified via bundle inspection; worth a visual pass on the preview deploy

🤖 Generated with Claude Code