dsh-wallpaper-engine liquid glass + settings toggle

Diff cards go liquid glass under dsh-wallpaper-engine

While a wallpaper is live, diff cards used to sit as opaque dark slabs over the wallpaper. The plugin now watches body[data-we-wallpaper] (the attribute dsh-wallpaper-engine sets while a wallpaper is rendered) and toggles a did-we-themed marker on <html> — the same pattern as the existing dsh-stylevault support. While the marker is on, the stylesheet adopts the plugin's own conversation glass recipe:

• translucent surface and header driven by --we-glass-alpha (surface ×0.8, header ×1.0, matching the plugin's bubble/composer weights), so the wallpaper shows through
• the same frosted backdrop-filter (blur(--we-blur) + saturate + brightness + contrast), specular sheen and glass shadow — the cards track the plugin's 玻璃 sliders live, including dark scheme
• without backdrop-filter support the card reverts to the opaque stock recipe so code stays readable
• placed after the stylevault block, so wallpaper glass wins the cascade

New setting: Wallpaper glass (壁纸玻璃)

The plugin settings card gains an On/Off row for the adaptation, persisted as inline-diff.wallpaper (default on), wired through the same plumbing as the other prefs. The Plugins-page settings card itself is untouched: under the glass settings window it already inherits the dialog treatment, and its own blur would double-frost.

pnpm test covers the new row (36 PASS / 0 FAIL).