Use FUSE 3 AppImage runtime for Linux packaging

[Copilot]

Neuron’s Linux AppImage currently uses the legacy AppImage runtime, which fails on modern distros that ship FUSE 3 but not libfuse.so.2. This updates packaging so generated AppImages use the newer FUSE 3-compatible runtime path.

• AppImage packaging
  • Upgrade electron-builder to a version with AppImage toolset selection.
  • Enable the FUSE 3 AppImage toolset:

toolsets:
  appimage: "1.0.2"

• Builder compatibility

  • Move Windows signing options under signtoolOptions to match the newer electron-builder schema.
  • Pin @electron/rebuild via Yarn resolutions to keep installs compatible with the repo’s Node version.

• Coverage

  • Add a focused packaging config test to guard the AppImage target and FUSE 3 toolset selection.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• registry.npmmirror.com
  • Triggering command: /usr/local/bin/node node /usr/local/bin/yarn install --frozen-lockfile (dns block)
• www.electron.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)