Feature Request: UI language localization / Soporte de idioma en la interfaz

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

All CLI interface strings (confirmation dialogs, system prompts, error messages)
are hard-coded in English with no way to change them. Messages like
"This command requires approval" or "Do you want to proceed?" cannot be
localized, even when the AI responses are configured in another language via
CLAUDE.md. This creates an inconsistent experience for non-English speakers.

Proposed Solution

Add a language or locale setting in settings.json or via an environment
variable (e.g. CLAUDE_LANG=es) to display CLI interface strings in the
user's preferred language, with English as the default fallback.

Alternative Solutions

• Respect the operating system's locale/language setting automatically.
• Allow community-contributed locale files (locales/es.json, locales/fr.json, etc.)

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

A Spanish-speaking developer in Latin America uses Claude Code daily.
While Claude responds in Spanish via CLAUDE.md, every system confirmation
dialog appears in English, breaking the flow of work.

Additional Context

Claude's AI responses already support any language through CLAUDE.md instructions.
Extending this to the CLI interface itself would make the tool fully accessible
to a global audience.