fix(release): publish auto-update metadata via electron-builder

[johannesjo]

Summary

• Switch both build jobs in .github/workflows/release.yml from electron-builder --publish never to --publish always so electron-builder's GitHubPublisher uploads latest-mac.yml, latest-linux.yml, the macOS .zip, and .blockmap files alongside the binaries.
• Drop the now-redundant softprops/action-gh-release upload steps; their globs only matched *.dmg/*.AppImage/*.deb and silently dropped the updater metadata.
• Keep the upfront create-release job so auto-generated release notes still land first; electron-builder finds the existing draft by tag and reuses it.

Why

In-app auto-update on macOS 404s on https://github.com/johannesjo/parallel-code/releases/download/v<ver>/latest-mac.yml (#168). The electron-updater client (electron/ipc/updater.ts) and build.publish config in package.json are both correct — only the workflow was dropping the metadata. Verified by listing v1.10.0 assets: only *.deb, *.dmg, *.AppImage were uploaded; no latest-*.yml, no *-mac.zip, no *.blockmap.

The new pattern is what the electron-builder docs recommend and is forward-compatible with v27 (which deprecates implicit --publish).

Notes for shipping

• This PR fixes v1.10.1+ onwards. Existing v1.10.0 installs will keep 404'ing until users manually upgrade — uploading a hand-crafted latest-mac.yml retroactively requires byte-identical artifacts that we no longer have.
• Token: uses the default secrets.GITHUB_TOKEN. permissions: contents: write is already set on the workflow.

Test plan

• Tag a release candidate (e.g. v1.10.1-rc.1) and confirm latest-mac.yml, latest-linux.yml, *-mac.zip, and *.blockmap all appear in the release assets.
• Install the previous version locally, then trigger the in-app update check and confirm it no longer 404s and offers the new version.
• Confirm the auto-generated release notes from the create-release job are still present (electron-builder should reuse the draft, not overwrite the body).