feat(2meet-data-optimizer-hivepress-addon): flatten a site's own listing attributes on opt-in

- the tmdo_hp_listing_attribute_fields filter (hp_ key => type) registers a
  site's HivePress listing attributes, such as a "Warranty" number attribute
  (hp_warranty, 901k rows on dev36), in their own hp_listing_attrs group: a
  new table with each column indexed at creation; hp_listing_core and its
  pinned hash are unchanged
- keys another group manages, keys without the hp_ prefix and unknown types
  are ignored
- Verify: HivePressEntityGroupsTest (opt-in, filtering, pinned hashes), unit
  147, integration 53, phpcs; dev36 hp_warranty backfill and queries
- PR: PR-109

includes/class-tmdo-hivepress-entity-groups.php

@@ -76,6 +76,7 @@ final class TMDO_HivePress_Entity_Groups {
 		self::register_hp_request_core_group();
 		self::register_hp_vendor_core_group();
 		self::register_hp_user_group();
+		self::register_hp_listing_attributes_group();
 	}
 
 	// ── Group definitions ────────────────────────────────────────────────────
@@ -271,6 +272,39 @@ final class TMDO_HivePress_Entity_Groups {
 			)
 		);
 	}
+	/**
+	 * A site's own HivePress listing attributes (created under Listings →
+	 * Attributes, e.g. a "Warranty" number → hp_warranty), opt-in through the
+	 * `tmdo_hp_listing_attribute_fields` filter: `array( 'hp_warranty' => 'integer' )`.
+	 *
+	 * They get a group of their own — a new table, each column indexed at
+	 * creation — so hp_listing_core and its pinned definition stay unchanged.
+	 * Keys another group already manages, keys without the hp_ prefix and
+	 * unknown types are ignored. Backfill with `wp tmdo post-migrate-group`.
+	 *
+	 * @return void
+	 */
+	private static function register_hp_listing_attributes_group(): void {
+		$fields = array();
+		foreach ( (array) apply_filters( 'tmdo_hp_listing_attribute_fields', array() ) as $key => $type ) {
+			$key = (string) $key;
+			if ( 1 !== preg_match( '/^hp_[a-z0-9_]+$/', $key )
+				|| ! in_array( $type, TMDO_Entity_Registry::VALID_TYPES, true )
+				|| null !== TMDO_Entity_Registry::get_field( 'post', $key, 'hp_listing' ) ) {
+				continue;
+			}
+			$fields[] = array(
+				'key'        => $key,
+				'type'       => $type,
+				'searchable' => true,
+				'label'      => 'Site listing attribute',
+			);
+		}
+		if ( $fields ) {
+			TMDO_Entity_Registry::register_group( 'post', 'hp_listing_attrs', $fields, array( 'post_types' => array( 'hp_listing' ) ) );
+		}
+	}
+
 	/**
 	 * HivePress request core meta keys (post_type=hp_request).
 	 *