fix: harden sing-box egress rollout

tests/test_uri.py

@@ -50,6 +50,10 @@ class UriParserTests(unittest.TestCase):
         endpoint = parse_hysteria2_uri("hysteria2://alice%3Acorrect%20horse@example.com")
         self.assertEqual(endpoint.password, "alice:correct horse")
 
+    def test_percent_encoded_at_is_preserved(self) -> None:
+        endpoint = parse_hysteria2_uri("hysteria2://alice%40example@example.com")
+        self.assertEqual(endpoint.password, "alice@example")
+
     def test_unicode_host_is_idna(self) -> None:
         endpoint = parse_hysteria2_uri("hysteria2://secret@пример.рф")
         self.assertEqual(endpoint.server, "xn--e1afmkfd.xn--p1ai")
@@ -89,6 +93,7 @@ class UriParserTests(unittest.TestCase):
             ("hysteria2://secret@example.com?pinSHA256=x", "safely"),
             ("hysteria2://secret@example.com?ech=x", "safely"),
             ("hysteria2://sec%ZZret@example.com", "percent"),
+            ("hysteria2://alice@example@server.example", "percent-encoded"),
             ("hysteria2://secret@example.com?sni=%FF", "UTF-8"),
         ]
         for uri, marker in cases: