The appearance route now opens with the design layout: serif "GENERAL"
overline + "Appearance" headline + intro paragraph, a four-tile
wallpaper picker (Dawn/Violet/Mint/Slate with active outline + check
glyph), a theme-mode segmented control, an accent swatch row, a
reduce-motion toggle, and a reset row. Every control mutates real state
through new shell methods (set_wallpaper_theme, set_theme_mode,
toggle_reduce_motion, reset_appearance) which delegate to the core.
The chrome lives in chrome::appearance_form so the page module is a
six-line shim. Light/Dark theme buttons currently switch the persisted
mode; rendering swaps will land when light/dark token sheets ship —
keeping the persistence so the eventual flip is one place.