v5.20-SONN

style: normalize main.yml to LF line endings

This workflow was the only text file in the repo committed with CRLF;
all 53 other tracked files are LF. There is no .gitattributes and
core.autocrlf is unset, so nothing normalizes on checkout.

Whitespace-only change; Actions parses either ending.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>