refactor: split VariableRef into ControlChars and DynamicContentRules (H2)

- ControlChars::strip()/stripDeep() (was VariableRef::withoutControls/Deep) with
  the S32/S32a/S35 docblock; callers AttrWriter, ShortformWriter, TextReplacer and
  the setting cleaner use it.
- DynamicContentRules (design system + dynamic content map): fieldsFor() (was
  contentFields: meta prefix -> map -> loop_ -> design names -> unknown),
  cleanSetting() (was setting(): raw strip -> raw marker -> field type ->
  final-string check -> meta key check, same order), one private method per
  field family (textSetting, selectPostSetting, scalarSetting), isMetaKey(),
  checkMap(), and the constants DEFAULT_DYNAMIC_CONTENT, META_SETTINGS,
  DESIGN_SETTINGS, META_KEY.
- VariableRef keeps the syntax: const END = ')$' replaces the six literals,
  payloadOf() is shared by typeOf() and canonical(); unknownName() is public for
  the rules. Error messages unchanged.
Tests unchanged apart from a class name in DynamicContentMapTest.

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

src/Integrations/Divi/Pages/DynamicContentMap.php

@@ -6,24 +6,24 @@ namespace LIT\MCP\Integrations\Divi\Pages;
 
 use Closure;
 use LIT\MCP\Integrations\Divi\Compose\Placeholders;
-use LIT\MCP\Integrations\Divi\Compose\VariableRef;
+use LIT\MCP\Integrations\Divi\Compose\DynamicContentRules;
 use LIT\MCP\Log;
 use Throwable;
 
 /**
- * VariableRef's dynamic content allow map (ruling S22) from Divi's live registry
+ * DynamicContentRules' dynamic content allow map (ruling S22) from Divi's live registry
  * DynamicContentOptions::get_options($postId, 'edit') – the options the Visual Builder offers
  * for this entry (filter divi_module_dynamic_content_options; the list depends on the post:
  * post_categories/post_tags only for types with those taxonomies). Shape:
  * option name => [setting key => field type], e.g. post_date => [before => richtext, …,
- * date_format => select]. VariableRef routes each setting by that type and keeps its fixed
+ * date_format => select]. DynamicContentRules routes each setting by that type and keeps its fixed
  * rules whatever the map says (enable_html refused, meta keys S29/S30, no markers S28).
  *
  * - loop_* options never enter the map: Divi offers them only inside loop-enabled modules,
- *   which the tools do not track – VariableRef refuses them ("nur innerhalb von Divi-Schleifen").
- * - The map REPLACES VariableRef's default, so every Placeholders::POST option is added when
- *   the registry lacks it, with the settings the placeholders write (VariableRef's default).
- * - Registry unavailable (no Divi, empty, error): null – VariableRef's default map applies.
+ *   which the tools do not track – DynamicContentRules refuses them ("nur innerhalb von Divi-Schleifen").
+ * - The map REPLACES DynamicContentRules' default, so every Placeholders::POST option is added when
+ *   the registry lacks it, with the settings the placeholders write (DynamicContentRules' default).
+ * - Registry unavailable (no Divi, empty, error): null – DynamicContentRules' default map applies.
  *
  * Not final so abilities can be tested with a fake registry.
  */
@@ -38,7 +38,7 @@ class DynamicContentMap
     {
     }
 
-    /** @return array<string, array<string, string>>|null Null = use VariableRef's default map. */
+    /** @return array<string, array<string, string>>|null Null = use DynamicContentRules' default map. */
     public function forPost(int $postId): ?array
     {
         try {
@@ -74,7 +74,7 @@ class DynamicContentMap
         }
 
         foreach (Placeholders::POST as $option) {
-            $map[$option] = ($map[$option] ?? []) + (VariableRef::DEFAULT_DYNAMIC_CONTENT[$option] ?? []);
+            $map[$option] = ($map[$option] ?? []) + (DynamicContentRules::DEFAULT_DYNAMIC_CONTENT[$option] ?? []);
         }
 
         return $map;
@@ -85,7 +85,7 @@ class DynamicContentMap
      * outputs them as HTML (DynamicContentElements::get_wrapper_element, wp_kses by the author's
      * unfiltered_html), and sanitize_text_field() would trim their meaningful spaces ("Von ").
      * html() is kses for editors, the S28 marker checks hold either way. No readable type: '' –
-     * VariableRef's strictest branch (a scalar without markup).
+     * DynamicContentRules' strictest branch (a scalar without markup).
      */
     private static function type(string $key, mixed $field): string
     {