home: Sort leading emoji first in channel names

Update the channel sorting logic to ensure streams with leading emojis
in their names are listed above those without emojis. The updated
sorting respects pinned, muted, and unmuted streams while handling
emoji precedence and maintaining alphabetical order for ties.

Fixes: zulip#1202

Author: lakshya1goel

lib/widgets/subscription_list.dart

@@ -45,11 +45,35 @@ class _SubscriptionListPageBodyState extends State<SubscriptionListPageBody> wit
     list.sort((a, b) {
       if (a.isMuted && !b.isMuted) return 1;
       if (!a.isMuted && b.isMuted) return -1;
+      
+      final isEmojiA = _startsWithEmoji(a.name);
+      final isEmojiB = _startsWithEmoji(b.name);
+      if (isEmojiA != isEmojiB) {
+        return isEmojiA ? -1 : 1;
+      }
+
       // TODO(i18n): add locale-aware sorting
       return a.name.toLowerCase().compareTo(b.name.toLowerCase());
     });
   }
 
+  bool _startsWithEmoji(String name) {
+    final firstChar = name.characters.first;
+    final int firstCharCode = firstChar.runes.first;
+
+    return (firstCharCode >= 0x1F600 && firstCharCode <= 0x1F64F) || // Emoticons
+        (firstCharCode >= 0x1F300 && firstCharCode <= 0x1F5FF) || // Misc Symbols and Pictographs
+        (firstCharCode >= 0x1F680 && firstCharCode <= 0x1F6FF) || // Transport and Map
+        (firstCharCode >= 0x1F700 && firstCharCode <= 0x1F77F) || // Alchemical Symbols
+        (firstCharCode >= 0x2600 && firstCharCode <= 0x26FF) || // Misc Symbols
+        (firstCharCode >= 0x2700 && firstCharCode <= 0x27BF) || // Dingbats
+        (firstCharCode >= 0xFE00 && firstCharCode <= 0xFE0F) || // Variation Selectors
+        (firstCharCode >= 0x1F900 && firstCharCode <= 0x1F9FF) || // Supplemental Symbols and Pictographs
+        (firstCharCode >= 0x1FA70 && firstCharCode <= 0x1FAFF) || // Symbols and Pictographs Extended-A
+        (firstCharCode >= 0x1F1E6 && firstCharCode <= 0x1F1FF) || // Flags
+        (firstCharCode >= 0x1F000 && firstCharCode <= 0x1FFFF); // Supplementary Multilingual Plane
+  }
+
   @override
   Widget build(BuildContext context) {
     // Design referenced from:

test/widgets/subscription_list_test.dart

@@ -150,6 +150,32 @@ void main() {
       ]);
       check(listedStreamIds(tester)).deepEquals([2, 1, 3, 4, 6, 5]);
     });
+
+    testWidgets('channels with emoji in name are listed above non-emoji names', (tester) async {
+      await setupStreamListPage(tester, subscriptions: [
+        eg.subscription(eg.stream(streamId: 1, name: '😊 Happy Stream')),
+        eg.subscription(eg.stream(streamId: 2, name: 'Alpha Stream')),
+        eg.subscription(eg.stream(streamId: 3, name: '🚀 Rocket Stream')),
+        eg.subscription(eg.stream(streamId: 4, name: 'Beta Stream')),
+      ]);
+
+      check(listedStreamIds(tester)).deepEquals([1, 3, 2, 4]);
+    });
+
+    testWidgets('channels with emoji in name, pinned, unpinned, muted, and unmuted are sorted correctly', (tester) async {
+      await setupStreamListPage(tester, subscriptions: [
+        eg.subscription(eg.stream(streamId: 1, name: '😊 Happy Stream'), pinToTop: true, isMuted: false),
+        eg.subscription(eg.stream(streamId: 2, name: '🚀 Rocket Stream'), pinToTop: true, isMuted: true),
+        eg.subscription(eg.stream(streamId: 3, name: 'Alpha Stream'), pinToTop: true, isMuted: false),
+        eg.subscription(eg.stream(streamId: 4, name: 'Beta Stream'), pinToTop: true, isMuted: true),
+        eg.subscription(eg.stream(streamId: 5, name: '🌟 Star Stream'), pinToTop: false, isMuted: false),
+        eg.subscription(eg.stream(streamId: 6, name: '🔥 Fire Stream'), pinToTop: false, isMuted: true),
+        eg.subscription(eg.stream(streamId: 7, name: 'Gamma Stream'), pinToTop: false, isMuted: false),
+        eg.subscription(eg.stream(streamId: 8, name: 'Delta Stream'), pinToTop: false, isMuted: true),
+      ]);
+
+      check(listedStreamIds(tester)).deepEquals([1,3,2,4,5,7,6,8]);
+    });
   });
 
   testWidgets('unread badge shows with unreads', (tester) async {