Feature request: Configurable language for Rindpeck companion

Summary

The Rindpeck companion (the penguin sidebar widget) always displays messages in English.
For non-English users, it would be great to have a configurable language option.

## Use case

I work entirely in Portuguese (pt-BR) — my CLAUDE.md sets "Responder sempre em português (pt-BR)".
Claude's responses respect this, but Rindpeck's messages remain in English, creating an inconsistent experience.

## Proposed solution

Allow configuring Rindpeck's language via one of:

• A companionLanguage field in settings.json
• Inheriting the language from CLAUDE.md instructions
• A global locale setting (e.g., CLAUDE_LOCALE=pt-BR)

## Additional context

This would benefit all non-English speaking users who configure Claude Code for their native language.