test(privacy): Count me is held to its last choice on the device that made it

Seed 77 found the phone showing Count me on after the laptop turned it
off: the instance withheld the laptop's row from the phone and handed back
the phone's own older one. That is a device held at an earlier genuine
record, ADR 0019's residual risk; what holds is that no device goes back
behind what it saw itself, which is what the test now checks.

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/learn/halkyon_learn_flutter/test/core/privacy/hostile_instance_test.dart

@@ -143,8 +143,9 @@ final class _World(
   final allowed = <String>{};
   var _next = 0;
 
-  /// Whether the person last turned Count me on.
+  /// Whether the person last turned Count me on, and on which device.
   bool countMe = false;
+  _Device? _countMeOn;
 
   // The instance's memory.
   final _history = <String, List<Object>>{};
@@ -664,6 +665,7 @@ final class _World(
       );
     }
     countMe = on;
+    _countMeOn = device;
     log.add('  Count me ${on ? 'on' : 'off'}');
   }
 
@@ -1181,8 +1183,13 @@ final class _World(
       }
     }
     // As the settings repository folds the rows the device reads: Count me
-    // on only where every one says so.
-    final device = _pick([laptop, phone]);
+    // on only where every one says so. On the device that made the last
+    // choice: any device can be held at an earlier genuine record (the
+    // instance withholding a newer one), but none behind its own.
+    final device = _countMeOn;
+    if (device == null) {
+      return null;
+    }
     final rows = [
       for (final row in await device.settings.rows())
         if (_decoded(row.payload) case final Map<String, Object?> settings)