feat: lit/divi-insert and lit/divi-update

All-or-nothing at ability level (S39), duplicate ids refused (S14),
set and attrs on the same path refused (S38), invalid_attr_path error.

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

src/Integrations/Divi/Compose/ShortformWriter.php

@@ -72,6 +72,25 @@ final class ShortformWriter
         return ['attrs' => $attrs, 'errors' => $errors];
     }
 
+    /**
+     * Attribute paths the given short-form fields of $type write to (unknown fields left out).
+     *
+     * @param list<string> $names Field names.
+     * @return array<string, string> Field => attribute path.
+     */
+    public function paths(string $type, array $names): array
+    {
+        $fields = $this->modules === null ? ShortformMap::fields($type) : ($this->modules[$type] ?? []);
+        $paths = [];
+        foreach ($names as $name) {
+            if (isset($fields[$name]['path'])) {
+                $paths[$name] = (string) $fields[$name]['path'];
+            }
+        }
+
+        return $paths;
+    }
+
     /**
      * The short-form color check (ruling S13; Task 3 reuses it for background_color): a
      * placeholder or reference that is a color reference, or a plain CSS color – checked