feat(web): move legal/terms and legal/privacy onto the dictionary spine (#5337)

[Lstarsky0]

Summary

legal/terms and legal/privacy were still forking their page chrome on
isZh. The strings move to legal-terms.ts / legal-privacy.ts behind
getLegalTerms / getLegalPrivacy, held to the page-body contract next to the
changelog. Copy is verbatim.

The terms themselves stay where they are. They are English for every locale on
purpose, and the zh page says the English text is the binding one, so they are
not dictionary copy.

The effective-date line used to be two translated fragments around
{LEGAL_UPDATED} in the JSX. It is now one fill() template, and a new test
keeps {date} in both locales so a translation can't quietly drop the date off
a legal page.

CEILING goes to 15, the count the test now reports.

check-locales.mjs now lists both new files, plus docs-work.ts, which the
docs/work migration left out.

No-Issue: two pages of the #5337 umbrella, which stays open.

Testing

Web only, no Rust touched. From web/:

• npm test — 491 passed
• npm run check — clean
• node scripts/check-locales.mjs — passes, and fails if zh drops a key or {date}

Rendered output, main vs this branch, both pages in all 18 locales: body text
and <title>/description/og:/twitter: meta identical. As a control, the
same comparison flags a single removed space after 于 in the zh date line, and
a one-character change to the zh description.

Checklist

• This PR adds a new layer/module/abstraction — n/a
• Updated docs or comments as needed — n/a
• Added or updated tests where relevant
• Verified TUI behavior manually if UI changes — n/a
• Harvested/co-authored credit uses a GitHub numeric noreply address

[github-actions]

Thanks @Lstarsky0 for taking the time to contribute.

This repository is observing a maintainer-managed PR intake gate in dry-run mode, so this pull request is staying open. This note helps maintainers prepare the allowlist before any enforcement is considered.

Please read CONTRIBUTING.md for the expected contribution shape. A maintainer can grant recurring PR access by commenting /lgtm on a pull request.