feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/features/channels/mentions/mention_ranking.dart

@@ -0,0 +1,104 @@
+import 'package:flutter/foundation.dart';
+
+/// A mention autocomplete candidate. Mirrors the desktop's
+/// `MentionCandidateForRanking` (desktop/src/features/messages/lib/mentionRanking.ts).
+@immutable
+class MentionCandidate {
+  final String pubkey;
+  final String? displayName;
+  final String? secondaryLabel;
+  final String? avatarUrl;
+  final bool isAgent;
+  final bool isMember;
+  final String? role;
+  final String? ownerPubkey;
+
+  const MentionCandidate({
+    required this.pubkey,
+    this.displayName,
+    this.secondaryLabel,
+    this.avatarUrl,
+    this.isAgent = false,
+    this.isMember = false,
+    this.role,
+    this.ownerPubkey,
+  });
+
+  String get label {
+    final name = displayName?.trim();
+    if (name != null && name.isNotEmpty) return name;
+    return pubkey.length >= 8 ? pubkey.substring(0, 8) : pubkey;
+  }
+}
+
+/// Group rank: channel members, then people, then other agents.
+/// Mirrors desktop's `getMentionCandidateGroupRank` (personas are a
+/// desktop-only concept; their slot between members and people is unused
+/// here so numbering stays aligned).
+int _groupRank(MentionCandidate candidate) {
+  if (candidate.isMember) return 0;
+  if (!candidate.isAgent) return 2;
+  return 3;
+}
+
+/// Match-quality score for one label. Lower is better; null means no match.
+/// Mirrors desktop's `scoreMentionCandidateLabel`.
+int? _scoreLabel(String label, String lowerQuery) {
+  final lower = label.toLowerCase();
+  if (lower == lowerQuery) return 0;
+  if (lower.startsWith(lowerQuery)) return 1;
+
+  final words = lower.split(RegExp(r'[\s\-_]+')).where((w) => w.isNotEmpty);
+  if (words.any((word) => word == lowerQuery)) return 2;
+  if (words.any((word) => word.startsWith(lowerQuery))) return 3;
+
+  return null;
+}
+
+/// Rank candidates for a mention query. Mirrors desktop's
+/// `rankMentionCandidates`: sort by group, then match quality, then the
+/// stable original order.
+List<MentionCandidate> rankMentionCandidates(
+  List<MentionCandidate> candidates,
+  String query,
+) {
+  final lowerQuery = query.toLowerCase();
+
+  final ranked = <(MentionCandidate, int, int, int)>[];
+  for (var order = 0; order < candidates.length; order++) {
+    final candidate = candidates[order];
+
+    final labelScores = [candidate.displayName, candidate.secondaryLabel].map((
+      value,
+    ) {
+      final trimmed = value?.trim();
+      if (trimmed == null || trimmed.isEmpty) return null;
+      return _scoreLabel(trimmed, lowerQuery);
+    }).whereType<int>();
+    int? score = labelScores.isEmpty
+        ? null
+        : labelScores.reduce((a, b) => a < b ? a : b);
+
+    if (score == null) {
+      final pubkeyLower = candidate.pubkey.toLowerCase();
+      if (pubkeyLower.startsWith(lowerQuery)) {
+        score = 4;
+      } else if (pubkeyLower.contains(lowerQuery)) {
+        score = 5;
+      }
+    }
+
+    if (score == null) continue;
+    ranked.add((candidate, _groupRank(candidate), score, order));
+  }
+
+  ranked.sort((a, b) {
+    final group = a.$2.compareTo(b.$2);
+    if (group != 0) return group;
+    final score = a.$3.compareTo(b.$3);
+    if (score != 0) return score;
+    return a.$4.compareTo(b.$4);
+  });
+
+  return [for (final item in ranked) item.$1];
+}