Refactor: locale-aware VMs, dictionary-driven views, and TopPage decomposition

[zigzagdev]

Content

• Threads Locale through the heritage VM mappers so English mode no longer falls back to Japanese strings, and adds displayName / displaySubName / displayDescription so view components can drop
  their own locale === "ja" branches.
• Pulls every visible string in the heritage detail panel, search form, top-page header, and result list out into the useText() dictionary; adds dictionary entries for both en and ja, plus per-value lookup tables for Category (Cultural / Natural / Mixed) and Region (Africa / Asia / Europe / …).
  • Decomposes TopPage into TopPageTitleBar, HeritageList, and TopPagePagination, leaving TopPage as a thin slot-based shell with four ReactNode slots and no named Props type. Extracts the locale flag toggle into a shared <LocaleToggle /> and reuses it in both the top page and the detail layout.
  • Cleans up Props placement in .tsx files: drops export type ...Props from TopPage, HeritageSubHeader, HeritageMetadataList, and SearchResultsPage; renames useText() results from t to
    text throughout the detail components.

Locale plumbing (mappers + hooks)

• toWorldHeritageVm / toWorldHeritageDetailVm / toHeritageSearchResultVm now take a locale argument and resolve title, subtitle, country, and the new displaySubName / displayDescription
  fields per locale.
• use-top-page and use-world-heritage-detail read locale via useLocale() and feed it to the mappers; SearchHeritageResultsContainer does the same.
  • Renamed the previously misnamed to-world-heritage-detail-vm-test.ts to .test.ts so it actually runs in Jest, and updated assertions for the new signature.

Dictionary-driven views

• New ui-text keys for sidebar labels, the search form, sort/reload controls, the locale toggle, app title/tagline, plus categoryLabels and regionLabels lookup tables. ja labels follow common Japanese heritage-site wording (e.g. 保有国, 分類, 遺産の面積, 文化遺産 / 自然遺産 / 複合遺産).
• HeritageSidebar, HeritageDetailLayout (KeyExamInfo), HeritageHero, HeritageOverviewSection,HeritageSearchForm, and TopPageTitleBar now read every label, placeholder, aria-label, and value from useText(). The brand string World Heritage is intentionally left untranslated in ja.

Structural cleanup

• New components: TopPageTitleBar, HeritageList, TopPagePagination, LocaleToggle. TopPage becomes { titleBar, header?, content, pagination? } of ReactNodes.
• TopPageContainer now constructs each subcomponent and wires it in.
• Test mocks for TopPageContainer retargeted at the new subcomponents.
• Dropped exported view-Props types in tsx files; renamed t → text for useText() consumers.

Notes

• Search results page Region/Category enum values (Asia, Cultural, …) used in the map popup and HeritageCard chip are still in English; out of scope for this PR.
• Locale is still resolved from the lang query param (e.g. ?lang=ja); switching to a path prefix is tracked separately.

Test plan

• npm run typecheck passes
• npm test passes (13 suites / 65 tests)
• Manual: open /heritages with ?lang=ja and ?lang=en, toggle via the new LocaleToggle, confirm header / search form / cards / detail panel / sidebar all switch.
• Manual: navigate /heritages/:id, confirm title / subtitle / overview / sidebar metadata are localized, and that the brand World Heritage stays English in both locales.
  このまま貼ればそのまま使えます。base ブランチは main 想定で書いてあります (もし develop 等なら適宜)。

[zigzagdev]

LGTM