style(desktop): unify Input/Textarea/SelectTrigger on shared controlVariants

Mirror the buttonVariants exercise for non-composer form controls: add a
single controlVariants source of truth (2.5px radius, 12px text,
padding-driven sizing, chrome via desktop-input-chrome) and consume it from
Input, Textarea, and SelectTrigger. Drop per-call radius/height/font
overrides that fought the shared look.

apps/desktop/src/components/ui/textarea.tsx

@@ -2,13 +2,12 @@ import * as React from 'react'
 
 import { cn } from '@/lib/utils'
 
-function Textarea({ className, ...props }: React.ComponentProps<'textarea'>) {
+import { type ControlVariantProps, controlVariants } from './control'
+
+function Textarea({ className, size, ...props }: React.ComponentProps<'textarea'> & ControlVariantProps) {
   return (
     <textarea
-      className={cn(
-        'desktop-input-chrome min-h-16 w-full rounded-md border px-3 py-2 text-sm outline-none placeholder:text-muted-foreground disabled:cursor-not-allowed disabled:opacity-50',
-        className
-      )}
+      className={cn(controlVariants({ size }), 'min-h-16', className)}
       data-slot="textarea"
       {...props}
     />