fix(HEL-560): 问天冻结区不再被陈旧样式清理波及

上一提交为过 CSS 门禁删掉了 heaven/foundation.css 里一条已无人引用的 .model.on，
但问天是冻结区，不该为了门禁变绿去动它。改为把冻结样式表从"每条选择器都要有
运行时消费者"这一项里排除，文件本身恢复原样；其余门禁照常覆盖问天。

Co-authored-by: multica-agent <github@multica.ai>

tests/test_css_governance.py

@@ -37,6 +37,10 @@ MODULE_STYLESHEETS = (
     "pages/review/foundation.css",
 )
 
+# 问天是冻结区：即便某条规则在当前运行时里已经没人引用，也不在这里做陈旧清理，
+# 免得为了让门禁变绿去动冻结代码。其余门禁（归属唯一、无空声明等）照常覆盖它。
+FROZEN_STYLESHEETS = ("pages/heaven/foundation.css",)
+
 RETIRED_STYLESHEETS = (
     "styles/styles.css",
     "styles/renovation.css",
@@ -559,6 +563,8 @@ class CssGovernanceTests(unittest.TestCase):
     def test_every_selector_has_a_runtime_consumer(self) -> None:
         stale: list[str] = []
         for relative, keys in self.rule_keys.items():
+            if relative in FROZEN_STYLESHEETS:
+                continue
             for contexts, selector in keys:
                 if selector.lower().startswith(("@keyframes", "@-webkit-keyframes")):
                     continue