Add a DayNight module (src/modules/daynight) exposing eve.DayNight() to script:
- A 24-hour clock (configurable speed / pause) derives the sun elevation and
azimuth each frame, repositioning the directional light so the sun sweeps the
sky over the day and fades to zero below the horizon.
- A procedural IBL sky cubemap (sky gradient + sun disc + deterministic night
stars) is regenerated per sun-angle bucket and registered as the 3D env map,
so both the skybox angle and the reflected sky follow the sun.
- Night light systems, each a set of Light3D entities toggled by name:
moonlight (cool directional), starlight (ambient boost), fire (warm point
light at a set position) and fireflies (a ring of gently-drifting points).
Add examples/daynight: a 3D diorama with a UI panel and hotkeys to pause/speed
the clock and toggle moonlight, fire and fireflies.
Add test/daynight.cpp (9 cases) and docs/usr/modules/daynight.md. Verified with
a syntax-only compile per the weather module precedent.
sunxfancy