fix(desktop): show the connecting splash when the local backend is slow to start

When the primary backend misses its readiness timeout and no main window
exists yet, show the connecting splash instead of leaving the desktop
windowless. The splash says "Starting T3 Code…" unless the boot is
WSL-only, where it keeps "Connecting to WSL…".

Fixes #23372

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
b76378b836Julius Marminge committed on 10/22/2026, 12:30:15 PMparentde87828
3 files changedLine totals unavailable