fix(MessageComposer): keep textarea focus ring suppressed after width fix

Loosening the .str-chat__textarea selector dropped its specificity from
(0,3,1) to (0,2,1), which let the global `.str-chat *:focus-visible`
outline rule (base.scss, (0,3,0)) override the textarea's `outline: none`
and show a focus ring. Re-assert the reset on :focus-visible so it lands at
(0,3,1) and keeps outranking the global outline.

Author: oliverlaz

src/components/MessageComposer/styling/MessageComposer.scss

@@ -267,6 +267,15 @@
       outline: none;
       width: 100%;
       scrollbar-width: none;
+
+      // The composer intentionally has no focus ring on the textarea itself.
+      // Re-assert the reset on :focus-visible so it keeps outranking the global
+      // `.str-chat *:not(:disabled):focus-visible` outline (base.scss, (0,3,0))
+      // now that this rule is scoped one level shallower (was (0,3,1) under
+      // .str-chat__message-composer-controls, now (0,2,1)).
+      &:focus-visible {
+        outline: none;
+      }
     }
   }