feat(classifier): label 'drop' via hard-rule + score threshold (-5 default)

- Add DEFAULT_THRESHOLDS['drop'] = -5 and DEFAULT_HARD_DROP_RULES const
- Add evaluate_hard_drop(): fires when no positive signals + short latin name OR ≥3 placeholder fields
- Wire into classify(): drop overrides all other labels; synthetic reason explains trigger
- Add drop_reason_label() and 'drop' => '⛔ авто-дроп' to MessageFormatter::LABEL_MAP
- Update ClassifierTest/MessageFormatterTest to extend Cf7stgTestCase (filter isolation)
- Adjust pre-existing assertions that now correctly yield 'drop' instead of 'spam'

includes/class-classifier.php

@@ -20,6 +20,12 @@ final class Classifier
     public const DEFAULT_THRESHOLDS = [
         'client' => 3,
         'spam'   => -2,
+        'drop'   => -5,
+    ];
+
+    public const DEFAULT_HARD_DROP_RULES = [
+        'short_latin_name'   => true,
+        'placeholder_fields' => true,
     ];
 
     public const DEFAULT_KEYWORDS = [
@@ -153,9 +159,28 @@ final class Classifier
             $label = 'spam';
         }
 
+        // Drop has highest priority (overrides client/unclear/spam/honeypot)
+        $is_drop_by_rule  = self::evaluate_hard_drop($fields);
+        $is_drop_by_score = isset($thresholds['drop']) && $score <= (int)$thresholds['drop'];
+        if ($is_drop_by_rule || $is_drop_by_score) {
+            $label = 'drop';
+            $reasons[] = ['sign' => '×', 'weight' => 0, 'text' => self::drop_reason_label($fields, $thresholds, $is_drop_by_rule)];
+        }
+
         return ['score' => $score, 'label' => $label, 'reasons' => $reasons];
     }
 
+    private static function drop_reason_label(array $fields, array $thresholds, bool $by_rule): string
+    {
+        if ($by_rule) {
+            $hits = [];
+            if (self::has_short_latin_name($fields)) $hits[] = 'короткое латинское имя';
+            if (self::count_placeholder_fields($fields) >= 3) $hits[] = '≥3 поля-плейсхолдера';
+            return 'hard-rule: ' . implode(' + ', $hits);
+        }
+        return 'score ≤ ' . (int)$thresholds['drop'];
+    }
+
     private static function concat_fields(array $fields): string
     {
         $out = [];
@@ -307,4 +332,35 @@ final class Classifier
         }
         return $count;
     }
+
+    /**
+     * Hard-rule decision: returns true if the submission has zero positive signals
+     * (no cyrillic name, no meaningful text, no valid email anywhere) AND at least
+     * one trigger fires (short latin name OR ≥3 placeholder fields).
+     *
+     * Triggers can be disabled individually via filter `cf7stg_hard_drop_rules`.
+     *
+     * @param array<string,string|string[]> $fields CF7 posted_data
+     * @return bool True if the submission should be silently dropped by hard-rule.
+     */
+    public static function evaluate_hard_drop(array $fields): bool
+    {
+        $rules = apply_filters('cf7stg_hard_drop_rules', self::DEFAULT_HARD_DROP_RULES);
+
+        // Любой позитивный сигнал — НЕ drop
+        $name = self::pick_field($fields, ['your-name', 'name', 'имя', 'fio']);
+        if ($name === '') $name = FieldDetector::find_name($fields);
+        if ($name !== '' && self::is_cyrillic_name($name)) return false;
+
+        $message = self::pick_field($fields, ['your-message', 'message', 'comment', 'сообщение', 'вопрос']);
+        if ($message !== '' && self::is_meaningful_text($message)) return false;
+
+        if (self::has_valid_email_anywhere($fields)) return false;
+
+        // Триггеры
+        if (!empty($rules['short_latin_name']) && self::has_short_latin_name($fields)) return true;
+        if (!empty($rules['placeholder_fields']) && self::count_placeholder_fields($fields) >= 3) return true;
+
+        return false;
+    }
 }