fix: stop guessing a kind for composite Divi attribute paths

Review fix round 1 on the lit/divi-catalog task:
- AttrPathIndex::collectKinds() no longer records a kind from a
  component.type === "group" node (a composite of several sub-kinds,
  e.g. button.innerContent = text + link + target), and kinds() now
  drops any attrName with more than one distinct candidate kind
  instead of last-write-wins (e.g. imageIcon.innerContent had onoff +
  icon + image sub-fields sharing one attrName). Both previously
  produced a wrong-but-present kind, which is more dangerous for 2b's
  sanitization routing than "unknown". Verified against the committed
  blurb/button/fullwidth-header fixture entries and live against the
  full 100-module catalog.
- AttrPathIndex::fromDefaults() now builds on AttrMap::flatten()
  instead of a parallel walker.
- ModuleCatalog::shortName() replaces the duplicated
  substr($name, strlen('divi/')) in DiviCatalogAbility.

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

src/Integrations/Divi/Schema/ModuleCatalog.php

@@ -46,6 +46,12 @@ final class ModuleCatalog
         return str_contains($type, '/') ? $type : 'divi/' . $type;
     }
 
+    /** "divi/button" → "button" (inverse of normalize(), for ShortformMap's short names). */
+    public static function shortName(string $name): string
+    {
+        return str_starts_with($name, 'divi/') ? substr($name, strlen('divi/')) : $name;
+    }
+
     public function has(string $name): bool
     {
         return isset($this->modules[$name]);