chore: drop POC-misleading transient SQL in uninstall

Persistent object caches store transients outside wp_options, so the
SQL DELETE patterns for _transient_page_for_* / _transient_timeout_*
were a partial cleanup at best — they ran on every uninstall but did
nothing useful on POC-enabled sites.

The mapping-driven loop above already calls delete_transient(), which
is POC-aware, so known-CPT transients are correctly cleaned in both
storage modes. The SQL fallback is now narrowed to orphan page_for_*
options only, with a comment explaining why transient orphans aren't
covered.

Author: nlemoine

uninstall.php

@@ -14,7 +14,8 @@
 }
 
 // Walk the aggregated mapping to clear known per-CPT options and transients
-// via the WP API. This handles object caches and the alloptions cache.
+// via the WP API. delete_transient is the only viable path when a persistent
+// object cache is enabled, since transients then don't live in wp_options.
 $pfcptMapping = get_option('pages_for_custom_post_type', []);
 if (is_array($pfcptMapping)) {
     foreach (array_keys($pfcptMapping) as $pfcptPostType) {
@@ -30,14 +31,15 @@
 delete_option('pages_for_custom_post_type');
 delete_option('pfcpt_db_version');
 
-// Catch any orphaned rows in wp_options for CPTs no longer present in the
-// aggregated mapping (e.g. a CPT was unregistered without cleanup).
+// Catch any orphan page_for_* options for CPTs no longer in the aggregated
+// mapping. Transient orphans aren't covered: on sites with a persistent
+// object cache they don't have wp_options rows at all; on sites without one
+// the unbounded transients (set_transient(..., 0)) would persist, but this
+// is rare enough to accept rather than scan the whole options table.
 global $wpdb;
 $wpdb->query(
     $wpdb->prepare(
-        "DELETE FROM {$wpdb->options} WHERE option_name LIKE %s OR option_name LIKE %s OR option_name LIKE %s",
-        $wpdb->esc_like('page_for_') . '%',
-        $wpdb->esc_like('_transient_page_for_') . '%',
-        $wpdb->esc_like('_transient_timeout_page_for_') . '%'
+        "DELETE FROM {$wpdb->options} WHERE option_name LIKE %s",
+        $wpdb->esc_like('page_for_') . '%'
     )
 );