#22734 cmux-next sidebar: the Updated card is glass again

Takes back #22670's fill change: the Updated card had become near-opaque. Leo 2026-10-20: "we want a lot of glass... I hate opaque."

Was: the "Updated to Nightly · What's New" card at the bottom of the sidebar drew its 13% text tint over a 94% --page-elevated fill. #22670 added that fill because list rows showed through the card.

Now: the card draws the composer's glass surface again: 13% text tint, 18% hairline edge, opaque only under Reduce Transparency. Rows no longer show through, because #22670's other change (SidebarCardSlotMotion) gives the card its own room above the account row, so no row sits behind it. The CSS comment now says the card stays glass on purpose, and the gallery notes are back to describing the glass surface.

Observed / Not run

CSS and gallery notes only. The existing gallery entries card-wallpaper and card-no-highlights-wallpaper capture the card over a wallpaper on the Linux gallery run. Committed through the GitHub API because local git on the build Mac is stuck in disk wait, so the local web lint didn't run.

Changelog

Changed: the sidebar's Updated card is glass again.

Agent session: cosmic-gray

🤖 Generated with Claude Code

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Summary by cubic

Makes the sidebar's Updated card glass again. #22670 had made it near-opaque, drawing its 13% text tint over a 94% --page-elevated fill so list rows wouldn't show through; the card now draws the composer's glass surface again — 13% text tint with an 18% hairline edge, opaque only under Reduce Transparency. Rows no longer show through because #22670's other change (SidebarCardSlotMotion) gives the card its own room above the account row. Also updates the CSS comment and gallery notes to describe the glass surface; changes are CSS and gallery notes only, and lint wasn't run because the commit went through the GitHub API.