- Add build.ps1: one-shot PowerShell build with version from git tag
- winamp_path config is now optional; roadamp works with any running
  Winamp instance regardless of install location (FindWindow does the
  discovery). Path is only needed if roadamp should launch Winamp itself.
- Remove hardcoded C:\Program Files\Winamp default

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>