feat(classifier): count_placeholder_fields() helper for drop-logic

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/ClassifierDropTest.php

@@ -102,4 +102,43 @@ final class ClassifierDropTest extends Cf7stgTestCase
         $fields = ['your-name' => ['OB', 'MU']];
         self::assertFalse(Classifier::has_short_latin_name($fields));
     }
+
+    public function test_count_placeholder_fields_screenshot_1(): void
+    {
+        $fields = require __DIR__ . '/fixtures/spam-screenshot-1.php';
+        // text-785: OB(2), text-787: 70(2), text-786: BP(2), text-788: ZZ(2), text-789: QV(2)
+        // text-790: 10 цифр — не placeholder. acceptance-data: служебное → исключено.
+        self::assertGreaterThanOrEqual(3, Classifier::count_placeholder_fields($fields));
+    }
+
+    public function test_count_placeholder_fields_ignores_empty(): void
+    {
+        $fields = ['a' => 'AB', 'b' => '', 'c' => 'XY', 'd' => null, 'e' => 'CD'];
+        self::assertSame(3, Classifier::count_placeholder_fields($fields));
+    }
+
+    public function test_count_placeholder_fields_ignores_long_values(): void
+    {
+        $fields = ['a' => 'AB', 'b' => 'Hello world', 'c' => 'CD'];
+        self::assertSame(2, Classifier::count_placeholder_fields($fields));
+    }
+
+    public function test_count_placeholder_fields_ignores_service_keys(): void
+    {
+        $fields = [
+            'acceptance-data' => '1',
+            '_wpcf7' => 'AB',
+            '_wpcf7_unit_tag' => 'XY',
+            'g-recaptcha-response' => 'CD',
+            'real' => 'EF',
+        ];
+        self::assertSame(1, Classifier::count_placeholder_fields($fields));
+    }
+
+    public function test_count_placeholder_fields_ignores_non_alnum(): void
+    {
+        // Кириллица или с пробелами не считается placeholder
+        $fields = ['a' => 'Ия', 'b' => 'a b', 'c' => 'XY'];
+        self::assertSame(1, Classifier::count_placeholder_fields($fields));
+    }
 }