docs: add both language options to Installation section

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -19,6 +19,9 @@ A structured research workflow skill for Claude Code, supporting two-phase resea
 # English version
 cp -r skills/research-en ~/.claude/skills/research
 
+# Chinese version
+cp -r skills/research-zh ~/.claude/skills/research
+
 # Required: Install agent
 cp agents/web-search-agent.md ~/.claude/agents/
 ```

README.zh.md

@@ -19,6 +19,9 @@ Claude Code 的结构化调研工作流技能，支持两阶段调研：outline
 # 中文版
 cp -r skills/research-zh ~/.claude/skills/research
 
+# 英文版
+cp -r skills/research-en ~/.claude/skills/research
+
 # 必需：安装agent
 cp agents/web-search-agent.md ~/.claude/agents/
 ```