feat(update): add startup health rollback fuse

tests/test_gui.py

@@ -1646,6 +1646,7 @@ class GuiTests(TempDirMixin, unittest.TestCase):
             staged = SimpleNamespace(
                 version="1.2.0",
                 staging_dir=os.path.abspath(staging_root),
+                sha256="a" * 64,
             )
 
             def prepare(_metadata, _install_root, **callbacks):
@@ -1738,6 +1739,39 @@ class GuiTests(TempDirMixin, unittest.TestCase):
         self.assertEqual("重试", dialog.action_button.text())
         self.assertIsNone(dialog.thread)
 
+    def test_startup_update_gate_fuses_a_previously_failed_release(self):
+        captured = []
+
+        class FakeDialog:
+            def __init__(self, result, parent=None):
+                captured.append(result)
+
+            def exec(self):
+                return 0
+
+        result = update_check.UpdateCheckResult(
+            current_version="1.0.0",
+            checked=True,
+            forced=True,
+            latest_version="1.2.0",
+            download_url="https://cm.833729.com/cmshopee.zip",
+            sha256="a" * 64,
+            size_bytes=100,
+            package_format="cmshopee-portable-v1",
+            updater_protocol=1,
+        )
+        with mock.patch(
+            "app.gui.update_health.get_failed_release",
+            return_value={"reason": "新版未就绪"},
+        ):
+            allowed = gui._run_startup_update_gate(
+                checker=lambda: result,
+                dialog_factory=FakeDialog,
+            )
+
+        self.assertFalse(allowed)
+        self.assertIn("已停止重复安装", captured[0].automatic_update_error)
+
     def test_startup_update_gate_check_failure_allows_entry_and_logs(self):
         result = update_check.UpdateCheckResult(
             current_version="1.0.0",