feat: render flash messages as toasts

Co-Authored-By: Claude Opus 5 <[email protected]>

tests/EventListener/HtmxErrorFlashListenerTest.php

@@ -48,7 +48,7 @@ class HtmxErrorFlashListenerTest extends WebTestCase
         self::assertFalse($this->client->getResponse()->headers->has('HX-Retarget'));
 
         $this->client->request('GET', '/');
-        self::assertSelectorTextContains('#flashes', self::MESSAGE);
+        self::assertSelectorExists(self::toastSelector(self::MESSAGE));
     }
 
     /**
@@ -61,6 +61,15 @@ class HtmxErrorFlashListenerTest extends WebTestCase
         self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
 
         $this->client->request('GET', '/');
-        self::assertSelectorTextNotContains('#flashes', self::MESSAGE);
+        self::assertSelectorNotExists('#flashes [data-controller~="toast"]');
+    }
+
+    /**
+     * A flash carries its text in the Stimulus value that toast_controller hands to Toastify, so
+     * there is nothing to read as element text -- the element itself stays empty.
+     */
+    private static function toastSelector(string $message): string
+    {
+        return \sprintf('#flashes [data-controller~="toast"][data-toast-text-value*="%s"]', $message);
     }
 }