feat(ui): glass surfaces for selection menus and comment popovers

The chat selection menu (desktop pill and mobile sheet), the chat
comment input, the file-preview Comment pill, the shared inline comment
editor, and the composer's context chip preview popover now use the
same translucent blurred glass surface as the btw panel, keeping their
borders and soft shadow.

packages/ui/src/components/comments/FilePreviewCommentMenu.tsx

@@ -231,8 +231,8 @@ export function FilePreviewCommentMenu({ containerRef, filePath, fileContent }:
         <div
           className={cn(
             'flex items-center whitespace-nowrap',
-            'rounded-full border border-[var(--interactive-border)]',
-            'bg-[var(--surface-elevated)] shadow-[0_4px_16px_-4px_rgb(0_0_0_/_0.12)]',
+            'oc-glass-popover rounded-full border border-[var(--interactive-border)]',
+            'shadow-[0_4px_16px_-4px_rgb(0_0_0_/_0.12)]',
             'p-1',
           )}
         >

packages/ui/src/components/comments/InlineCommentInput.tsx

@@ -149,7 +149,7 @@ export function InlineCommentInput({
       onPointerDown={(e) => e.stopPropagation()}
       onTouchStart={(e) => e.stopPropagation()}
     >
-      <div className="rounded-xl border border-[var(--interactive-border)] bg-[var(--surface-elevated)] shadow-[0_4px_16px_-4px_rgb(0_0_0_/_0.12)]">
+      <div className="oc-glass-popover rounded-xl border border-[var(--interactive-border)] shadow-[0_4px_16px_-4px_rgb(0_0_0_/_0.12)]">
         {(fileLabel || displayRange) ? (
           <div className="flex items-center gap-2 px-3 pt-2 text-xs font-medium text-[var(--surface-mutedForeground)] opacity-60">
             {fileLabel ? <span className="max-w-[200px] truncate">{fileLabel}</span> : null}