mara: "swarm dash is in my own colors, but tab colors on swarm ui are
the default catpucchin one." Root cause: hive-c0re/theme.nix's stylix
overlay only ever wrote a themed colors.css onto the dashboard/agent
frontend subtrees -- swarm-ui, served from its own separate package,
was never in scope.
Extracts the stylix-detection + colors.css-generation logic (previously
inline in theme.nix) into a shared nix/host-modules/stylix-theme.nix,
imported by both theme.nix and swarm-ui.nix -- one source instead of a
second copy that has to agree by inspection. swarm-ui.nix gains its own
themedPackage overlay (same shape as theme.nix's themedFrontend: copy
the package, overwrite static/colors.css) and serves that instead of
cfg.package directly when stylix is active; a clean passthrough
otherwise.
Verified with a throwaway nixosSystem eval (this repo's own flake
checks do not exercise gateway-module wiring) confirming the unthemed
path resolves cfg.package unchanged.
2ecf842a1b