When the operator's host config has stylix enabled, generate a base16
colors.css from its palette and overlay it onto the bundled frontend dist,
then serve that themed tree as the dashboard's HIVE_STATIC_DIR. Zero-op
auto-detect — no flake input, no operator action, no npm/esbuild rebuild
(a pure file-copy over the prebuilt dist). colors.css is the whole swap
contract; theme.css derives the semantic vars from the 16 base16 slots.
Guarded access (config.lib.stylix / config.stylix.enable via 'or' fallbacks)
makes it a clean no-op when stylix isn't imported — HIVE_STATIC_DIR stays
on the unthemed dist, which is what every non-stylix deployment + CI gets.
Dashboard surface only for now; the agent surface needs the base16 palette
forwarded host->agent (the per-agent harness builds its own dist) and is a
separate follow-up.