od-unix: seed Qt launcher from default.uae at startup

od-unix: seed Qt launcher from default.uae at startup

The shared core loads <configurationpath>/default.uae into the prefs at
startup (main.cpp real_main), but the Qt launcher built its state from
scratch, so the default configuration had no visible effect unless the
GUI was disabled. Pass the file as the launcher's initial config path
when it exists, matching the Windows "save as default.uae" behavior.

Configs given on the command line keep precedence: the launcher's own
argument parsing decides, exposed through the bridge so gui_init does
not duplicate it. The bridge no longer infers runtime mode from "an
initial config path is present"; gui_display passes it explicitly.