refactor(ui): extract a shared drink-count pluralisation helper

The 'count == 1 ? drink : drinks' ternary was inlined at four call
sites, past the extract-a-helper threshold in AGENTS.md. The failure
mode is silent and accessibility-facing: a new label that forgets the
ternary announces "1 drinks" to a screen reader and nothing fails. Two
of the four sites had exactly that bug until review caught it in #506.

Adds StringFormattingHelper.drinkCountLabel and routes all four sites
through it. Labels are unchanged.

Fixes #513

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ER7MeRfgMqxnaKBGDaSRWy

Author: claude

lib/screens/my_festival_screen.dart

@@ -220,7 +220,7 @@ class _MyFestivalScreenState extends State<MyFestivalScreen> {
   Widget _buildSectionHeader(BuildContext context, String title, int count) {
     return Semantics(
       header: true,
-      label: '$title section, $count ${count == 1 ? 'drink' : 'drinks'}',
+      label: '$title section, ${StringFormattingHelper.drinkCountLabel(count)}',
       child: Padding(
         padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
         // Use the theme's titleLarge (the app's Playfair "poster" voice) rather

lib/utils/string_formatting_helper.dart

@@ -14,4 +14,14 @@ class StringFormattingHelper {
     if (text.isEmpty) return text;
     return text[0].toUpperCase() + text.substring(1);
   }
+
+  /// Format a drink count with the correctly pluralised noun.
+  ///
+  /// Used in screen-reader labels, where an inlined `count == 1 ? ... : ...`
+  /// ternary has twice been forgotten and announced '1 drinks' (#506, #513).
+  ///
+  /// Example: 0 -> '0 drinks', 1 -> '1 drink', 2 -> '2 drinks'
+  static String drinkCountLabel(int count) {
+    return '$count ${count == 1 ? 'drink' : 'drinks'}';
+  }
 }

lib/widgets/drink_filter_sheets.dart

@@ -113,8 +113,8 @@ class CategoryFilterSheet extends StatelessWidget {
                         );
                         return Semantics(
                           label:
-                              'Filter by $formattedCategory, $count '
-                              '${count == 1 ? 'drink' : 'drinks'}',
+                              'Filter by $formattedCategory, '
+                              '${StringFormattingHelper.drinkCountLabel(count)}',
                           value: isSelected ? 'Selected' : 'Not selected',
                           selected: isSelected,
                           button: true,
@@ -337,8 +337,8 @@ class StyleFilterSheet extends StatelessWidget {
                           final isSelected = selectedStyles.contains(style);
                           return Semantics(
                             label:
-                                'Filter by $style, $count '
-                                '${count == 1 ? 'drink' : 'drinks'}',
+                                'Filter by $style, '
+                                '${StringFormattingHelper.drinkCountLabel(count)}',
                             value: isSelected ? 'Selected' : 'Not selected',
                             selected: isSelected,
                             button: true,

lib/widgets/festival_header.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import '../models/models.dart';
 import '../providers/providers.dart';
+import '../utils/utils.dart';
 
 /// App-bar title for the drinks screen: app icon, current festival name, the
 /// drink count, and a coloured status badge.
@@ -17,8 +18,7 @@ class FestivalHeader extends StatelessWidget {
       provider.sortedFestivals,
     );
     final drinkCount = provider.drinks.length;
-    final drinkCountLabel =
-        '$drinkCount ${drinkCount == 1 ? 'drink' : 'drinks'}';
+    final drinkCountLabel = StringFormattingHelper.drinkCountLabel(drinkCount);
 
     // Fold the status into the label and exclude child semantics so screen
     // readers announce one coherent phrase instead of the name, count, and

test/string_formatting_helper_test.dart

@@ -28,5 +28,20 @@ void main() {
         expect(StringFormattingHelper.capitalizeFirst('a'), 'A');
       });
     });
+
+    group('drinkCountLabel', () {
+      test('pluralises zero', () {
+        expect(StringFormattingHelper.drinkCountLabel(0), '0 drinks');
+      });
+
+      test('uses the singular for exactly one', () {
+        expect(StringFormattingHelper.drinkCountLabel(1), '1 drink');
+      });
+
+      test('pluralises counts above one', () {
+        expect(StringFormattingHelper.drinkCountLabel(2), '2 drinks');
+        expect(StringFormattingHelper.drinkCountLabel(147), '147 drinks');
+      });
+    });
   });
 }