[AI Bundle] Skip processing empty store configurations

Fix the issue where configuring only one store type (e.g., chromadb)
would cause errors for other unconfigured store types. The configuration
system populates all store types with empty arrays by default, and the
processStoreConfig method was checking for package availability before
checking if any stores were actually configured.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: OskarStark

src/ai-bundle/src/AiBundle.php

@@ -979,6 +979,10 @@ private function processAgentConfig(string $name, array $config, ContainerBuilde
      */
     private function processStoreConfig(string $type, array $stores, ContainerBuilder $container, array &$setupStoresOptions): void
     {
+        if ([] === $stores) {
+            return;
+        }
+
         if ('azuresearch' === $type) {
             if (!ContainerBuilder::willBeAvailable('symfony/ai-azure-search-store', AzureSearchStore::class, ['symfony/ai-bundle'])) {
                 throw new RuntimeException('Azure Search store configuration requires "symfony/ai-azure-search-store" package. Try running "composer require symfony/ai-azure-search-store".');

src/ai-bundle/tests/DependencyInjection/AiBundleTest.php

@@ -717,6 +717,25 @@ public function testChromaDbStoreCanBeConfigured()
         $this->assertTrue($container->hasAlias('Symfony\AI\Store\StoreInterface'));
     }
 
+    #[TestDox('Configuring only one store type does not require packages for other store types')]
+    public function testConfiguringOnlyOneStoreTypeDoesNotRequireOtherStorePackages()
+    {
+        $container = $this->buildContainer([
+            'ai' => [
+                'store' => [
+                    'chromadb' => [
+                        'my_store' => [
+                            'collection' => 'test_collection',
+                        ],
+                    ],
+                ],
+            ],
+        ]);
+
+        $this->assertTrue($container->hasDefinition('ai.store.chromadb.my_store'));
+        $this->assertFalse($container->hasDefinition('ai.store.azuresearch.my_store'));
+    }
+
     public function testChromaDbStoreWithCustomClientCanBeConfigured()
     {
         $container = $this->buildContainer([