Add Korean (ko-KR) language specification

Summary

Adds Korean (ko-KR) as a new supported language in the GitLab Duo Agent Translation Platform.

Changes

New files

• specifications/languages/ko-kr/styleguide.md - Korean marketing style guide adapted from the tech-docs-ai-powered-translation Korean style guide, covering formality levels, grammar, cultural adaptations, and quality checklist.

• specifications/languages/ko-kr/termbase.csv - Korean terminology database (~450 terms). See construction details below.

Updated files

• system-prompt.md - Added Korean (ko-kr) resource URLs and ko-KR label to the supported languages list.

How the Korean termbase was constructed

1. The approved Crowdin glossary (termabse-crowdin.csv) was used as the authoritative source. This is a multi-language export from Crowdin containing translations for all GitLab-supported locales.
2. The Korean column (Term [ko]) was extracted into a smaller Korean-only file (termabse-crowdin-ko-only.csv) to work within tool size limits.
3. All Korean terms from the extracted file were mapped into the project's en-us,ko-kr termbase format (termbase.csv).
4. The intermediate Crowdin source files were removed, keeping only the canonical termbase.csv.