mara, on review: "i thought we just swap a css file via nginx
config?" -- right instinct. The package-copy overlay (cp -r + install)
only made sense for hive-c0re's servedFrontend, which backs multiple
serve points (dashboard root + every per-agent gateway route) from one
swapped tree. swarm-ui has exactly one location serving cfg.package, so
an = /static/colors.css exact-match override -- the same idiom every
other single-path override on this vhost already uses (/api/whoami,
/api/docs) -- replaces the whole derivation with one location block.
Verified with the same throwaway nixosSystem eval as the previous
commit: unthemed case has no colors.css location and the / root is
cfg.package unchanged.
10a294a2f8