fix: [hidden] must beat display:flex so archive/settings panels collapse

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BCrwHHnGCB5XH968Nxokqw

core/tests/Feature/InboxPageTest.php

@@ -96,6 +96,15 @@ class InboxPageTest extends TestCase
         $this->assertStringNotContainsString('class="counter"', $html);
     }
 
+    public function test_hidden_attribute_beats_flex_display_rules(): void
+    {
+        // .panel .body{display:flex} иначе перебивает браузерное [hidden]{display:none},
+        // и свёрнутые панели архива/настроек показываются всегда.
+        $html = $this->get('/', ['X-Remote-User' => 'nikita'])->assertOk()->getContent();
+        $this->assertStringContainsString('[hidden]{display:none!important}', $html);
+        $this->assertStringContainsString('<div class="body" hidden', $html);
+    }
+
     public function test_unsafe_deep_link_is_not_rendered_as_href(): void
     {
         $this->get('/', ['X-Remote-User' => 'nikita']);