feat(i18n): Native Brazilian Portuguese (pt-BR) Localization, Language Onboarding & UI Ergonomics

[OTheMandaloriano]

Summary

We have implemented complete, native support for Brazilian Portuguese (pt-BR) across the entire DeepSeek Harness monorepo, along with a first-launch language onboarding dialog featuring crisp vector flags (Lipis SVG) and ergonomic layout improvements.

Highlights

• 100% pt-BR Localization: Faithful native translation across 30+ client packages with complete technical context for all agent modes (Standard, PTC, Creator, Minimal).
• First-Launch Onboarding Dialog: Added LanguageOnboardingDialog allowing users to choose their language on first access.
• Settings UI Ergonomics: Expanded settings sidebar width from 188px to 245px so localized labels (like "Predefinições do agente") render without truncation.
• Full Documentation: Added complete README.pt-BR.md and updated headers passing all pairing consistency gates (verify-translation-pairing).

Links for Review & Cherry-Pick

• Fork Repository: https://github.com/OTheMandaloriano/deepseek-harness
• Feature Branch: https://github.com/OTheMandaloriano/deepseek-harness/tree/feat/pt-br-localization
• Release (v0.1.5-rc.2-ptbr): https://github.com/OTheMandaloriano/deepseek-harness/releases/tag/dsh-v0.1.5-rc.2-ptbr

All commits follow Conventional Commits and pass all Lefthook hooks, linters, and test suites. We would love to see this integrated into upstream!

[unera]

Related proposal, may matter for how this one ships: make the UI locale an ordered preference list (e.g. ru → en → zh) instead of a single choice, so a partly translated UI falls back to a language the user actually reads rather than to untranslated islands and Chinese source keys. It also keeps the shipped-locale set from being a closed enum.

Details and a link list of the other language threads: #11699