[Feature Request] /paste command doesn't work in WSL2

## Environment
- Q CLI v1.19.0
- Windows 11 + WSL2 Ubuntu 22.04

## Problem
`/paste` command fails in WSL2 with "No image found in clipboard" because WSL2 cannot access Windows clipboard for images.

## Expected
Support `/paste` in WSL2 by either:
1. Auto-detect WSL2 and use PowerShell bridge: `powershell.exe -Command "(Get-Clipboard -Format Image).Save('/tmp/paste.png')"`
2. Accept file path: `/paste /mnt/c/path/to/image.png`

## Impact
WSL2 is the only way to run Q CLI on Windows. This makes `/paste` unusable for all Windows users.