chore(ui): widen mention/plus dropdown to 420px

Long resource names were truncating in a 320px-wide menu. Bump to 420px and
cap with max-w on viewport so it can't overflow on small screens. Overrides
the emcn DropdownMenuContent's default max-w-[220px] via twMerge.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: TheodoreSpeaks

apps/sim/app/workspace/[workspaceId]/home/components/user-input/components/plus-menu-dropdown.tsx

@@ -245,7 +245,7 @@ export const PlusMenuDropdown = React.memo(
             side='top'
             sideOffset={8}
             avoidCollisions={!isMention}
-            className='flex w-[320px] flex-col overflow-hidden'
+            className='flex w-[420px] max-w-[calc(100vw-32px)] flex-col overflow-hidden'
             onCloseAutoFocus={handleCloseAutoFocus}
             onOpenAutoFocus={handleOpenAutoFocus}
             onKeyDown={handleContentKeyDown}