Revert Windows SignPath signing

[nwparker]

Summary

• reverts Sign Windows releases with SignPath #1300 and Fix signed Windows updater checksum metadata #1712
• restores Windows release publishing to the pre-SignPath electron-builder path
• removes SignPath signing, Slack approval notification, signed artifact staging, and checksum rewrite logic

Validation

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release-cut.yml"); puts "release-cut.yml parses"'\n- git diff --check origin/main...HEAD\n