[FEATURE] Japanese (日本語) localization for permission dialogs and UI

Feature Request

Description

Permission dialogs (Allow/Deny, tool approval prompts) and other UI elements in Claude Code are English-only. Japanese users would benefit from localized UI.

Use Case

• Japanese-speaking users (researchers, developers) frequently encounter permission dialogs
• Understanding "Allow once / Allow always / Deny" requires English comprehension
• Tool descriptions and confirmation messages would be clearer in the user's native language

Proposed Solution

• Add locale/language setting to Claude Code configuration
• Localize permission dialog text (Allow/Deny/Allow always etc.)
• Support at minimum: Japanese (ja), with framework for other languages

Environment

• macOS (Apple Silicon)
• Claude Code CLI
• User language: Japanese

Related

• Issue #21400 (Granular Language Customization) is related but focuses on chat vs code language, not UI localization