Pin every written-out copy of the rail's collapsed conditions

Plan step 36, navigation review. The Tailwind-era rail-collapsed:
variant is now plain selectors in 26 rules, each repeated in five
window bands, across navigation-rail.css, navigation-rail-item.css,
navigation-rail-section.css and layout/scaffold.css; the tests pinned
a few of them. A new test walks every rule whose :where() names the
rail and fails when a copy drifts from the seven conditions for its
band, or when a rule is drawn collapsed in some bands but not all five.
ComponentStylesheet gains rules() for it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

tests/Support/ComponentStylesheet.php

@@ -117,6 +117,17 @@ final class ComponentStylesheet
         return $declarations;
     }
 
+    /**
+     * Every rule, nesting resolved, in source order: for a test that has to walk all of them rather
+     * than name one.
+     *
+     * @return list<array{selector: string, at: list<string>, declarations: array<string, string>}>
+     */
+    public function rules(): array
+    {
+        return $this->rules;
+    }
+
     public function has(string $selector, array $at = []): bool
     {
         try {