dsh-wsl-mnt: Detect Slow Workspaces in WSL /mnt and Suggest Linux Paths

`dsh-wsl-mnt` is a client plugin for DeepSeek Harness (DSH) designed to address the low filesystem performance in WSL environments. It uses the `mnt_doctor` tool to automatically detect workspace paths, identify projects located in slow non-native Linux paths such as `/mnt/c` (NTFS) or Desktop, and issue warnings and migration suggestions to users, optimizing Git operations and development efficiency.