Add report UI locale support

[s133per]

Summary

• Add report UI language support for English, Simplified Chinese, Traditional Chinese, Spanish, German, and Japanese.
• Localize report chrome labels while preserving evaluator-generated findings as authored.
• Add localized README entry points for Chinese, Spanish, German, and Japanese.

Not done

• No machine translation of evaluator output, deductions, evidence, or recommendations.
• No runtime locale persistence beyond the existing report page language selector.

Evidence

• pnpm test
• pnpm --dir .agents/skills/ai-native-eval/scripts/eval test:browser
• pnpm render:example
• README locale link check
• git diff --check