Revert chrome-bg: sidebar/queue should just be the tinted background

Per feedback, the solid color-mix bar was wrong — sidebar, queue and
the mobile header should stay on the plain --mf-bg (the same subtly
hue-shifting black used everywhere else), exactly like light mode
already does, not a separately-boosted colored panel. Drop --mf-chrome-bg/
--color-chrome and switch those three back to bg-bg.

The general dark-mode richness bump (tc(), --mf-bg/--mf-elevated/etc.)
and the glass-bar background-color fix from the previous commit stay;
only the separate chrome treatment is reverted.

web-player/src/routes/layout.css

@@ -5,7 +5,6 @@
 	--font-display: 'Sora Variable', ui-sans-serif, system-ui, sans-serif;
 
 	--color-bg: var(--mf-bg);
-	--color-chrome: var(--mf-chrome-bg);
 	--color-elevated: var(--mf-elevated);
 	--color-surface: var(--mf-surface);
 	--color-surface-2: var(--mf-surface-2);