feat(i18n): add 9 language README translations (de, es, fr, it, ja, ko, pt, tr, vi)

Expand from 3 to 12 languages, matching oh-my-claudecode's coverage.
All 12 READMEs have consistent full language-switcher lines.

Constraint: Must match oh-my-claudecode's 12-language coverage
Confidence: high
Scope-risk: narrow

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Cerdore

README.de.md

@@ -5,7 +5,7 @@
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](LICENSE)
 [![CI](https://github.com/Cerdore/gdb-cli/actions/workflows/ci.yml/badge.svg)](https://github.com/Cerdore/gdb-cli/actions/workflows/ci.yml)
 
-[English](README.md) | [中文](README.zh-CN.md) | [Русский](README.ru.md)
+English | [한국어](README.ko.md) | [中文](README.zh-CN.md) | [日本語](README.ja.md) | [Español](README.es.md) | [Tiếng Việt](README.vi.md) | [Português](README.pt.md) | [Русский](README.ru.md) | [Türkçe](README.tr.md) | [Deutsch](README.de.md) | [Français](README.fr.md) | [Italiano](README.it.md)
 
 A GDB debugging tool designed for AI Agents (Claude Code, etc.). Uses a "thin client CLI + GDB built-in Python RPC Server" architecture, enabling stateful GDB debugging through Bash.