Two post-rebase regressions from the round-10 index.css merge:

- The merge seam ate the closing brace of .chat-composer-glass, silently
  nesting the entire composer-glass section (shell, host, context strip,
  shoulder tab, banner cap) inside it as descendant rules that never
  matched — the composer surface stopped painting and thread content
  showed straight through the input. The brace is restored and the
  compensating over-close removed; every composer selector emits at top
  level again.

- The thread-details popover grew dropdown-glass card chrome around the
  panel: round 9 deleted the legacy components-layer .dropdown-glass rule
  in favor of the @utility, which the popover's border-0/bg-transparent
  suppressors no longer outrank (the utility emits later in the layer).
  The suppressors are now important variants, matching the !overflow
  override already there.

Verified against the emitted production CSS: shell::before is top-level,
no descendant-of-glass selectors remain, and the important suppressors
(including [backdrop-filter:none]!) are emitted.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>