action_sheet: Use directional border radius for reaction buttons

Previously, the reaction buttons in the message action sheet used
hardcoded physical border radii. In RTL locales, this caused the
rounded corners to appear on the inner edges of the button row
instead of the outer edges.

We now use  and resolve it against the
context's text direction to ensure the correct corners are rounded
regardless of layout direction.

Author: yash-agarwa-l

lib/widgets/action_sheet.dart

@@ -1229,11 +1229,12 @@ class ReactionButtons extends StatelessWidget {
     required bool isFirst,
   }) {
     final designVariables = DesignVariables.of(context);
+    final textDirection = Directionality.of(context);
     return Flexible(child: InkWell(
       onTap: () => _handleTapReaction(emoji: emoji, isSelfVoted: isSelfVoted),
       splashFactory: NoSplash.splashFactory,
       borderRadius: isFirst
-        ? const BorderRadius.only(topLeft: Radius.circular(7))
+        ? const BorderRadiusDirectional.only(topStart: Radius.circular(7)).resolve(textDirection)
         : null,
       overlayColor: WidgetStateColor.resolveWith((states) =>
         states.any((e) => e == WidgetState.pressed)
@@ -1253,6 +1254,7 @@ class ReactionButtons extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final textDirection = Directionality.of(context);
     final store = PerAccountStoreWidget.of(pageContext);
     final popularEmojiCandidates = store.popularEmojiCandidates();
     assert(popularEmojiCandidates.every(
@@ -1289,7 +1291,7 @@ class ReactionButtons extends StatelessWidget {
         InkWell(
           onTap: _handleTapMore,
           splashFactory: NoSplash.splashFactory,
-          borderRadius: const BorderRadius.only(topRight: Radius.circular(7)),
+          borderRadius: const BorderRadiusDirectional.only(topEnd: Radius.circular(7)).resolve(textDirection),
           overlayColor: WidgetStateColor.resolveWith((states) =>
             states.any((e) => e == WidgetState.pressed)
               ? designVariables.contextMenuItemBg.withFadedAlpha(0.20)