- Add updater.go for managed plugin auto-update (version check, download,
Y/n prompt, zip extraction with zip-slip protection)
- Add stdio.go transport for local MCP server subprocess communication
via stdin/stdout JSON-RPC 2.0
- Implement InstallFromGit in loader.go with URL parsing for HTTPS/SSH
- Wire up --git flag in plugin install command
- Switch all plugin CLI output to English (headers, status, messages)
- Add tests for parseGitURL and promptUpdate