Comb/Index::delete() rewrites the entire JSON file even when the document was never indexed

[SUXUMI]

Bug description

Statamic\Search\Comb\Index::delete() always calls $this->save($data) after $data->forget($ref), regardless of whether the reference was actually present in the index data. Because Laravel Collection::forget() is silent when the key is absent (vendor/laravel/framework/src/Illuminate/Collections/Collection.php:1997-1999 - unset($this->items[$key]) on a missing key is a no-op), the code rewrites the entire index JSON file to disk for no semantic reason whenever delete() is called for a document that was never in the index.

// vendor/statamic/cms/src/Search/Comb/Index.php:89-100  (v6.14.0; same on 5.x)
public function delete($document)
{
    try {
      $data = $this->data();
    } catch (IndexNotFoundException $e) {
       return;
    }

      $data->forget($document->getSearchReference());
      $this->save($data);   // ← unconditional full-file rewrite
}

The downstream call site that triggers this hot path is Statamic\Search\Search::updateWithinIndexes( (vendor/statamic/cms/src/Search/Search.php:57-71):

  $this->indexes()->each(function ($index) use ($searchable) {
      $shouldIndex = $index->shouldIndex($searchable);
      $exists = $index->exists();

      if ($shouldIndex && $exists) {
          $index->insert($searchable->getSearchReference());
      } elseif ($shouldIndex && ! $exists) {
          $index->update();
      } elseif ($exists) {
          $index->delete($searchable);   // ← fires for EVERY existing index that doesn't contain this entry
      }
  });

Proposed fix:

   public function delete($document)
   {
       try {
           $data = $this->data();
       } catch (IndexNotFoundException $e) {
           return;
       }

  -    $data->forget($document->getSearchReference());
  -    $this->save($data);
  +    $ref = $document->getSearchReference();
  +
  +    if (! $data->has($ref)) {
  +        return;                                                                                                                                                                                                               
  +    }
  +
  +    $data->forget($ref);
  +    $this->save($data);
   }

How to reproduce

1. Install Statamic v6, default local search driver
2. Configure two indexes at least, in config/statamic/search.php, scoped to separated collections - e.g. news and pages
3. Run php artisan statamic:search:update news and php artisan statamic:search:update pages to build index files in storage/statamic/search/
4. Observe disk I/O while saving e.g. news entry

Sample code for tinker/Tinkerwell

config(["queue.default" => "sync"]);

$entry = Entry::query()
    // ->where("collection", "news")
    ->where("id", <new-entry-id>)
    ->first();

$pagesPath = storage_path("statamic/search/pages.json");
clearstatcache();
$mtimeBefore = filemtime($pagesPath);

$entry->slug(time() . "-testing");
$entry->save();

clearstatcache();
$mtimeAfter = filemtime($pagesPath);

echo "pages.json mtime changed: " .  ($mtimeBefore !== $mtimeAfter ? "YES (BUG)" : "NO") 

Result: absolutely all *.json files will be modified!

Environment

- Statamic version: 6.14.0
- Same code present on 5.x branch (src/Search/Comb/Index.php:89-100)
- Laravel: 12.56.0
- PHP: 8.4.20

Installation

Existing Laravel app