docs: update troubleshooting with idempotent PATH commands (#95)

- Use correct PATH pattern matching syntax
- Explain installer auto-adds PATH
- Provide idempotent command for manual use

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Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

README.md

@@ -371,11 +371,14 @@ setx PATH "%USERPROFILE%\bin;%PATH%"
 
 **Codex wrapper not found:**
 ```bash
-# Check PATH
-echo $PATH | grep -q "$HOME/.claude/bin" || echo 'export PATH="$HOME/.claude/bin:$PATH"' >> ~/.zshrc
-
-# Reinstall
+# Installer auto-adds PATH, check if configured
+if [[ ":$PATH:" != *":$HOME/.claude/bin:"* ]]; then
+    echo "PATH not configured. Reinstalling..."
     bash install.sh
+fi
+
+# Or manually add (idempotent command)
+[[ ":$PATH:" != *":$HOME/.claude/bin:"* ]] && echo 'export PATH="$HOME/.claude/bin:$PATH"' >> ~/.zshrc
 ```
 
 **Permission denied:**

README_CN.md

@@ -307,11 +307,14 @@ setx PATH "%USERPROFILE%\bin;%PATH%"
 
 **Codex wrapper 未找到：**
 ```bash
-# 检查 PATH
-echo $PATH | grep -q "$HOME/.claude/bin" || echo 'export PATH="$HOME/.claude/bin:$PATH"' >> ~/.zshrc
-
-# 重新安装
+# 安装程序会自动添加 PATH，检查是否已添加
+if [[ ":$PATH:" != *":$HOME/.claude/bin:"* ]]; then
+    echo "PATH not configured. Reinstalling..."
     bash install.sh
+fi
+
+# 或手动添加（幂等性命令）
+[[ ":$PATH:" != *":$HOME/.claude/bin:"* ]] && echo 'export PATH="$HOME/.claude/bin:$PATH"' >> ~/.zshrc
 ```
 
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