Remove focus-visible border from composer container

The container uses a steady hairline border (no focus/click flash), with focus-visible styling delegated to the inner textarea. The container is a layout wrapper, not a focus target.

src/renderer/src/components/native-chat/NativeChatComposerField.tsx

@@ -122,11 +122,11 @@ export function NativeChatComposerField({
           <div
             data-native-file-drop-target={NATIVE_FILE_DROP_TARGET.composer}
             className={cn(
-              // Why: steady hairline fill (no click border flash); keyboard
-              // focus still shows via focus-visible on the inner textarea.
+              // Why: always-on hairline (token-level border, not focus ring) —
+              // no focus/click border flash. The box is a container, not a
+              // focus target.
               'rounded-lg border border-border p-1.5 shadow-xs',
-              'bg-muted/50 dark:bg-input/40',
-              'has-[:focus-visible]:border-ring'
+              'bg-muted/50 dark:bg-input/40'
             )}
           >
             {imageAttachments.length > 0 ? (