fix: empty status filter, hidden-field probing, own private posts

Review fix round 2: content-query no longer lets get_posts() fall back
to 'publish' when every requested status is capability-gated out (now
short-circuits to an empty page). Its field filter shares PostPresenter's
hidden-field rule (Pods password type, protected meta) so a hidden key
is rejected like an unknown one instead of reaching the query. Password
fields are now type-checked as strings on write. A user without
edit_private_posts can still query their own private posts when the
query is already author-restricted, matching WordPress core.

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

src/Integrations/WordPress/Content/PostPresenter.php

@@ -144,7 +144,7 @@ class PostPresenter
     {
         $result = [];
         foreach ($this->schema->fields((string) $post->post_type) as $key => $field) {
-            if ($this->isHidden($field)) {
+            if (self::isHiddenField($field)) {
                 continue;
             }
 
@@ -158,9 +158,11 @@ class PostPresenter
      * Pods password fields and readonly protected meta (WordPress' own "_"-prefixed
      * internal keys) are never read out via lit-content-get/-query: neither belongs in
      * front of the model, and both are one plugin registration away from leaking secrets
-     * or internal engine state.
+     * or internal engine state. Public and static so ContentQueryAbility can apply the
+     * same rule to its `field` filter – a hidden field must be as unreachable through the
+     * query filter as it is through the fields map, or the filter becomes a probe.
      */
-    private function isHidden(FieldDefinition $field): bool
+    public static function isHiddenField(FieldDefinition $field): bool
     {
         if ($field->type === 'password') {
             return true;