The build config only had a Windows target. Adds a linux block producing
an AppImage, plus a 512x512 build/icon.png so the packaged app does not
ship with the stock Electron icon.
Verified by running the packaged binary: the embedded server comes up on
9095 and serves the overlay from process.resourcesPath, confirming the
extraResources mapping works in a packaged build.
StartupWMClass is deliberately not set via linux.desktop -- electron-builder
already emits the correct value, and the nested { entry: {...} } form leaks a
literal "entry=[object Object]" line into the .desktop file.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
shadowdaoandClaude Opus 5
d8107a06c2