fix(mountain-view): plain sheet under the conversation, round avatar button

Under the message the reply buttons sat on the tinted strip the default
layout uses for its quick reply, a different colour from the message
above them in the light theme. Mountain View now reads the whole
conversation on the page colour.

The account avatar in the top bar got a square highlight while every
other button there is round.

components/email/email-viewer.tsx

@@ -4066,8 +4066,10 @@ export function EmailViewer({
         </div>
       )}
 
-      {/* Email Content Area */}
-      <div className={cn("flex-1 overflow-auto overscroll-contain bg-muted/30", isMobile && !mvMobileViewer && "pb-[calc(3.25rem+env(safe-area-inset-bottom)/2)] sm:pb-0")}>
+      {/* Email Content Area. Mountain View reads the conversation on one plain
+          sheet, so the reply buttons under the message sit on the page colour
+          rather than on a tinted strip. */}
+      <div className={cn("flex-1 overflow-auto overscroll-contain", mvViewer || mvMobileViewer ? "bg-background" : "bg-muted/30", isMobile && !mvMobileViewer && "pb-[calc(3.25rem+env(safe-area-inset-bottom)/2)] sm:pb-0")}>
       <div className="min-h-full flex flex-col">
 
       {/* === SENDER INFO (Desktop) === */}

components/layout/account-switcher.tsx

@@ -267,7 +267,9 @@ export function AccountSwitcher({
         data-testid="account-switcher"
         data-active-account-id={activeAccountId ?? undefined}
         className={cn(
-          "flex items-center gap-2 rounded-md transition-colors",
+          // Round under Mountain View, like every other button in its top bar.
+          "flex items-center gap-2 transition-colors",
+          mvPopover ? "rounded-full" : "rounded-md",
           variant !== "expanded"
             ? "justify-center w-10 h-10 hover:bg-muted"
             : "w-full px-2 py-1.5 hover:bg-muted text-start min-w-0",