Port the GitHub runner fix (d51bae7) to .gitea/workflows/build-macos.yml:
warm Finder/System Events before tauri build, and set
TAURI_BUNDLER_DMG_IGNORE_CI=true so create-dmg does not skip
AppleScript under CI=true. Tighten DMG/.app discovery to the
release bundle paths.
Closes#189 for the Gitea workflow.