Upstream 913977ec hard-wired set_darkmode() to dark and rewrote
web/mesh/index.css to be dark-only. Restored the dark-conditional body of
set_darkmode() from 913977ec^; the boot call now takes its arg from
MESH_TOOL_CONFIG.dark (parsed from a new cmms_dark=1|0 query param that
public/mesh-edit.php sets from theme_is_dark()), defaulting to dark when
absent so the freestanding app is unchanged. Added a scoped
#app:not(.dark) light-chrome layer to index.css (additive; never matches
in the always-dark freestanding app).