electron-builder 26.3.6 fixed auto-discovery for Developer ID certificates
but not for "3rd Party Mac Developer Application" certificates used in
MAS builds.
The after-pack.js script successfully finds and uses the MAS certificate
for signing the proxy binary, but electron-builder's own signing mechanism
fails to auto-discover it, falling back to ad-hoc signing.
Add explicit CSC_NAME env var to the MAS build step in the workflow to
tell electron-builder exactly which certificate to use.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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