fix(meditate): a chosen chip in Explore keeps its icon

The check Material draws on a chosen chip covered the category's or the
kind's icon. The chip's colour says it is chosen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/meditate/halkyon_meditate_flutter/test/app/meditate_app_test.dart

@@ -1282,6 +1282,19 @@ void main() {
       expect(find.text('Library credits'), findsNothing);
     });
 
+    testWidgets('a chosen chip keeps its icon: no check over it (the '
+        "developer's review, 5 Nov 2026)", (tester) async {
+      await exploreLibrary(tester);
+      await scrollTo(tester, find.text('From meditate.example.org'));
+      final chips = tester.widgetList<ChoiceChip>(
+        find.byWidgetPredicate(
+          (widget) => widget is ChoiceChip && widget.avatar != null,
+        ),
+      );
+      expect(chips, isNotEmpty);
+      expect(chips.every((chip) => chip.showCheckmark == false), isTrue);
+    });
+
     group('spoken languages (5 Nov 2026)', () {
       final german = LibraryItem(
         id: 'abendruhe',