fix: Task 6 review round 2 - builder column classes, sum check only for exact rows, unknown path wins, column structure text (S43)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Integrations/Divi/Compose/Composer.php

@@ -48,6 +48,12 @@ final class Composer
 
     private const DEFAULT_LEVEL = 'h2';
 
+    /**
+     * The builder's "Column Class" choices (Divi 5.2.1 visual-builder/build/field-library.js):
+     * n_24, the special fractions and "none" (no width class). Ruling S43.
+     */
+    private const COLUMN_CLASSES = ['1_5', '2_5', '3_5', '1_7', '1_9', '1_10', '1_11', 'none'];
+
     /** Advice of the S40 overlap error for new nodes. */
     private const ONE_FORM = 'für diesen Pfad nur Kurzform oder attrs angeben';
 
@@ -467,6 +473,13 @@ final class Composer
         }
 
         $result = $this->attrWriter->apply($name, $attrs, $spec['attrs'], $path . '.attrs');
+        // An unknown path is the more useful message on its key (it decides invalid_attr_path).
+        foreach ($result['invalid_paths'] as $invalid) {
+            $key = $path . '.attrs.' . $invalid;
+            if (isset($result['errors'][$key])) {
+                $this->errors[$key] = $result['errors'][$key];
+            }
+        }
         $this->errors += $result['errors'];
         array_push($this->invalidPaths, ...$result['invalid_paths']);
 
@@ -658,6 +671,17 @@ final class Composer
         return $error;
     }
 
+    /** Ruling S43: whether $width is a column class the Visual Builder offers. */
+    public static function isColumnClass(mixed $width): bool
+    {
+        if (! is_string($width)) {
+            return false;
+        }
+
+        return in_array($width, self::COLUMN_CLASSES, true)
+            || (preg_match('/^([1-9]|1\d|2[0-4])_24$/D', $width) === 1);
+    }
+
     /**
      * Whether the fractions add up to exactly 1: numerators scaled to the least common
      * denominator (denominators are divisors of 24 or 5, 7, 9, 10, 11 – at most 27720).