chore(2meet-data-optimizer): make the hardening branch pass PHPStan and PHPCS

- CI PHPStan (level 6, baseline for pre-existing debt) failed on 35 errors in
  code added on hardening/2.0: missing iterable value types (PHPDoc only), a
  redundant method_exists() in uninstall.php, and the new WP-CLI commands
  registered as array('Class', 'instanceMethod') — now array(new Class(), ...)
- Local runs had been masked by a PHPStan tmpDir shared with the act CI runner
  (cached container pointing at a removed phar); use a private tmpDir
- Verify: phpstan (private tmpDir) no errors, phpcs clean on changed files,
  phpunit Unit 658 OK; dev22 (running this branch) CLI post-status-sync /
  bridge-restore-native dry runs OK

includes/diagnostic/class-tmdo-site-health.php

@@ -442,7 +442,7 @@ class TMDO_Site_Health {
 	 * Not cached: the collision list is in-memory state rebuilt on every
 	 * request, so reading it is free and a transient would only go stale.
 	 *
-	 * @return array Site Health result.
+	 * @return array<string, mixed> Site Health result.
 	 */
 	public static function check_entity_group_collisions(): array {
 		$collisions = class_exists( 'TMDO_Entity_Registry' ) ? TMDO_Entity_Registry::get_collisions() : array();
@@ -482,7 +482,7 @@ class TMDO_Site_Health {
 	 *
 	 * Not cached for the same reason as check_entity_group_collisions().
 	 *
-	 * @return array Site Health result.
+	 * @return array<string, mixed> Site Health result.
 	 */
 	public static function check_orphaned_entity_groups(): array {
 		$restored = class_exists( 'TMDO_Entity_Registry' ) ? TMDO_Entity_Registry::get_restored_groups() : array();
@@ -521,7 +521,7 @@ class TMDO_Site_Health {
 	 *
 	 * Not cached: two class_exists() probes.
 	 *
-	 * @return array Site Health result.
+	 * @return array<string, mixed> Site Health result.
 	 */
 	public static function check_missing_integration_addons(): array {
 		$missing = class_exists( 'TMDO_Compatibility' ) ? TMDO_Compatibility::missing_integration_addons() : array();