fix(cache-on-save): latch page-cache invalidation to once per submit

onFormProcessed fires once per process action (add_page/upload/message/
reset), so the deleteAll() + Cache::invalidateCache() pair ran 4x per post.
Gate it behind a $cacheInvalidated latch (same pattern as $photosReconciled)
so the store wipe + system.yaml touch happen exactly once, and log the step.

Code review F1 (perf) + F7 (observability).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mpdu3Dt1iVoozHwAMyjrbn

plugins/cache-on-save/cache-on-save.php

@@ -25,6 +25,14 @@ class CacheOnSavePlugin extends Plugin
      */
     private bool $photosReconciled = false;
 
+    /**
+     * Same 4x-per-submit firing as $photosReconciled: onFormProcessed runs once
+     * per process action. Clearing the page-tree cache is idempotent, but doing it
+     * four times per post is wasted work (a full deleteAll() + system.yaml touch
+     * each time). Latch it so the invalidation runs exactly once per submission.
+     */
+    private bool $cacheInvalidated = false;
+
     public static function getSubscribedEvents(): array
     {
         return [
@@ -191,16 +199,22 @@ class CacheOnSavePlugin extends Plugin
             }
         }
 
-        // Two-part invalidation. deleteAll() drops the Doctrine store (the tracker
+        // Two-part invalidation, latched to run ONCE per submit (see
-        // feed page cache etc.), but the page-tree INDEX is keyed on
+        // $cacheInvalidated) — the 4 process actions would otherwise repeat it.
+        // deleteAll() drops the Doctrine store (the tracker feed page cache etc.),
+        // but the page-tree INDEX is keyed on
         // md5(dirs + folderHash + config->checksum() + lang) (Pages::buildRegularPages).
         // With cache.check.method:folder that index can survive a create — a fresh
         // entry then stays invisible to the API (GET /api/v1/pages{route} 404s), so
         // opening the just-posted entry for editing shows "this entry no longer
         // exists". invalidateCache() touches system.yaml, bumping config->checksum()
         // so the index key changes and the tree rebuilds on the next request.
+        if (!$this->cacheInvalidated) {
+            $this->cacheInvalidated = true;
             $this->grav['cache']->deleteAll();
             Cache::invalidateCache();
+            $this->grav['log']->info('cache-on-save: cleared page cache + invalidated page-tree index after new-entry submit');
+        }
     }
 
     /**