DeepSeek Harness Plugin: Fixing Chinese Character Garbling in pwsh

The pwsh tool in DeepSeek Harness (DSH) has an issue with garbled Chinese characters in Windows environments. This plugin, `hongweifei/dsh-pwsh-encoding-fix`, is designed to fix the problem. It performs encoding conversion within the PowerShell process, automatically detects mixed GBK and UTF-8 output, and ensures lossless capture. The plugin supports foreground and background commands. By default, it decodes using the system ANSI code page, while also allowing a specific code page to be forced through configuration. After installation, restart DSH Web for the changes to take effect. Be aware of special limitations related to the `Write-Host` and `exit` commands.