Summary

All runtime-configurable values in src/config.h are compiled-in:

• CONFIG_COMPOSITOR — hardcoded to "cosmic-session"
• CONFIG_DESKTOP_NAME — hardcoded to "cosmic"
• CONFIG_RESTART_DELAY — hardcoded to 2 seconds
• CONFIG_GREETER_CMD / CONFIG_GREETER_ARGS — hardcoded cage path

These should eventually be read from a config file (e.g. /etc/atrium.conf
or session .desktop files for the compositor), so atrium is not limited to
a single compositor.

Locations

• src/config.h:6 — top-level SHORTCUT comment
• src/config.h:9-43 — all hardcoded #define values

Notes

This is a larger feature: it implies defining a config file format, a parser,
and session .desktop discovery. Shelved until the core is stable.