site: fix Clients showcase, header copy, and footer

[makefunstuff]

Summary

• Fix broken Clients section: replace the collapsing 3-column grid with a CSS-only one-at-a-time showcase (segmented control: Harness | Neovim | VS Code) so mocks stay full-width and captions sit under the visible mock.
• Rewrite section header to plain copy: eyebrow Clients, h2 Same findings in a harness, Neovim, or VS Code.
• Move init.lua / require('jev').setup({}) into Start (stacked under cargo install) with section overflow: clip / isolation so nothing floats into Clients.
• Quieter footer: jev-lsp — MIT. Early PoC; APIs may change. Source on GitHub.

Test plan

• Open Pages preview / local site/ — Clients shows one mock at a time; tabs switch without JS
• Resize to mobile/tablet — no caption row / collapsed windows
• Scroll Clients → Start — init.lua stays in Start only
• Footer reads as one quiet line
• Dark cinematic look, amber accent only, no JS/CDN

Do not merge until reviewed.