chore: .gitignore 添加 .opencode/ 目录

安装 oh-my-opencode 插件后，排除 OpenCode 项目级配置目录，
避免影响团队其他成员。

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

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

Author: CodeCasterX

.gitignore

@@ -16,6 +16,9 @@ tmp/
 # Gemini
 .gemini-clipboard/
 
+# OpenCode
+.opencode/
+
 # Claude Code local settings
 **/settings.local.json