feat(site): add es/pt/it locale support with UI selector
- Expand runtime locale support from 2 to 5 locales (en, zh, es, pt, it)
- Add locale normalization/cycling logic and button labels
- Add Spanish/Portuguese/Italian UI text bundles
- Update localized labels for journey/audience/kind, reading paths,
command-lane hints, and engineering pillars
- Rework locale rendering with fallback helper for untranslated fields
- Update language toggle behavior in command palette
- Add localized README files (es, pt, it)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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