v0.8.59: Add next-wave README and website locales for Korean, Spanish, and Brazilian Portuguese

[Hmbown]

Problem

After website parity for existing README locales and Russian are tracked separately, CodeWhale should still have a practical next-wave localization pack for broader global reach.

The highest-leverage next set is:

• Korean (ko-KR or route ko)
• Spanish (es)
• Brazilian Portuguese (pt-BR)

These cover strong developer communities without requiring RTL layout work or a large number of simultaneous translation PRs.

Evidence

• README currently ships English, Simplified Chinese, Japanese, and Vietnamese only.
• Website currently ships English and Chinese only.
• v0.8.59: Define README + website localization matrix, source text, and drift checks #3090 tracks the localization matrix and selector/drift-check foundation.
• v0.8.59: Bring the website to parity with existing Japanese and Vietnamese README locales #3091 tracks website parity for existing Japanese and Vietnamese README translations.
• v0.8.59: Add Russian README and website localization with Cyrillic QA #3092 tracks Russian explicitly.
• There is no current issue for Korean, Spanish, or Portuguese README + website localization.

Proposed direction

Ship these as a reviewed translation wave after the foundation work is in place:

1. Korean (ko-KR README, /ko website route)
2. Spanish (es README, /es website route)
3. Brazilian Portuguese (pt-BR README, /pt-BR or /pt route per v0.8.59: Define README + website localization matrix, source text, and drift checks #3090)

This can be split into separate PRs per locale, but one issue should own the shared acceptance standard and ordering.

Translation guidelines:

• Keep commands, config keys, model IDs, provider IDs, env vars, and file paths literal.
• Preserve the v0.8.65 end-cap: Rewrite README with CodeWhale history, Fleet, and provider routing map #3087 factual history: deepseek-tui origin, Chinese community adoption, broader provider support, CodeWhale rename.
• Use natural technical wording, not literal machine translation.
• Keep provider/model support classifications consistent with README/provider docs: default, supported, experimental, self-hosted.

Acceptance criteria

• Korean README and website locale are added.
• Spanish README and website locale are added.
• Brazilian Portuguese README and website locale are added.
• Every new README is linked symmetrically from all README language headers.
• Website locale selector lists native language names for the new locales.
• Accept-Language detection recognizes ko, es, pt, and pt-BR appropriately.
• Install commands, provider IDs, model IDs, and env vars remain unchanged in all translations.
• Long translated text is checked at mobile and desktop widths for nav, buttons, cards, FAQ rows, and install tiles.
• Locale drift checks from v0.8.59: Define README + website localization matrix, source text, and drift checks #3090 include these locales before the issue is closed.

Verification

find . -maxdepth 1 -name 'README*.md' | sort
npm --prefix web run lint
npm --prefix web test -- --run
npm --prefix web run build

Manual checks:

1. Visit /ko, /es, and the chosen Portuguese route.
2. Use the locale selector from homepage, install, docs, FAQ, roadmap, and contribute pages.
3. Check mobile layout for text overflow.
4. Spot-check that commands and provider/model IDs are not translated.