fix(mcp): tint the companion's tool rows with the theme, not six fixed hues

Each tool group in the codeg-mcp popover carried a colour of its own —
blue, indigo, sky, emerald, violet, amber — which read as a paint chart
next to the switches and ignored the selected theme entirely. The six rows
now share one tile in `--primary`, so the list follows `[data-theme]`;
they are still told apart by icon shape and label.

In the grayscale themes this also lifts the glyph well clear of its tile,
where the amber and emerald rows had been the two least legible things in
the popover. The state badge and its dot keep their colours: those are a
fault signal, not decoration.