Translate the WebUI common.json to pt-BR, register the locale in
config.ts (with normalizeLocale rules for "pt", "pt-BR", "pt-PT", ...)
and index.ts resources, and add a Brazilian Portuguese overview
assertion in i18n.test.tsx.
Notes:
- Generic "pt" and any "pt-*" variant resolve to pt-BR. A future
pt-PT locale can be added without affecting existing users.
- Universally borrowed technical terms (nanobot, BYOK, MCP, JSON,
URL, Web, Apps when used as a product name, Skills) are kept in
English, matching the pattern used by es/fr/ja/ko/vi/id.
- Empty-thread greetings, quick-action prompts, and slash command
descriptions are translated; quick-action prompts are intentionally
phrased so the agent still receives a clear task spec.
Verified with bun run test (536 passing), bun run lint (clean), and
bun run build (7.18s).
