Window/taskbar icon never showed because the packaged .desktop had
StartupWMClass=ModelRouter while the live window WM_CLASS is the lowercase
app class 'modelrouter-gui' — no match, so GNOME fell back to the default
Electron icon.
- main.js: set BrowserWindow icon asset + backgroundColor (window paints
correctly with frameless titlebar and provides the taskbar's default icon)
- package.json: build.linux.desktop.entry.StartupWMClass now equals the real
WM_CLASS so packaged installs match too
- local integration: user-level .desktop installed at
~/.local/share/applications/modelrouter-gui.desktop (points at the unpacked
binary) so GNOME resolves the icon immediately
- coreReady now only flips after the embedded core actually answers HTTP
(fixes blank-screen race where the iframe loaded before the listener)
- renderer probes reachability, retries frame load with exponential backoff,
and recovers via onerror instead of giving up forever
- keep per-user theme in localStorage
- embedded profile no longer preconfigures a zen source (desktop users add
their own upstreams on the sources page)
