website: warn when JS is disabled that the console won't open

[okcodes]

Summary

• Adds a <noscript> banner above the nav that tells visitors with JS disabled the live console demo won't open (the rest of the page still works, per the prerendering in website: prerender to static HTML for no-JS crawlers/agents #31).
• Styled to match the existing design language: dark background, amber warning accent (distinct from the site's cyan brand color, so it reads as a notice), centered text, same max-w-6xl content width as the nav.
• Lives in index.html, outside the React tree, on purpose — a <noscript> wrapping JSX children in a hydrated React app is unreliable (React's hydration reconciliation ends up creating the children as real DOM nodes even with JS enabled, since React doesn't respect the HTML parser's noscript-content-as-text behavior). Keeping it as plain HTML sidesteps that entirely: React never touches it, and the browser's native noscript handling does the hiding.

Test plan

• Built the site and confirmed the amber Tailwind utility classes (bg-amber-400, border-amber-400, text-amber-200) made it into the compiled CSS — confirms Tailwind's content scan covers index.html.
• Loaded the built site in a browser with JS enabled — banner is correctly hidden, no console errors.
• pnpm run typecheck and pnpm run lint (oxlint, repo-wide) pass with no new warnings.
• Reviewer: disable JavaScript in a browser and load the deployed/preview site to see the banner render.

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