fix: 按 K-00 约定修复 Python SDK 断线重交与退避

sdk/python/src/nixmsg/protocol.py

@@ -46,13 +46,24 @@ def down_topic(endpoint_id: str) -> str:
     return f"nix/c/{endpoint_id}/down"
 
 
-def normalize_mqtt_ws_url(url: str) -> str:
-    """保证 WebSocket 路径以 /mqtt 结尾。"""
+def normalize_mqtt_ws_url(url: str, *, allow_tcp: bool = False) -> str:
+    """http→ws、https→wss；路径为空或 / 时用 /mqtt，否则保留；mqtt/mqtts 仅显式允许裸 TCP。"""
     raw = url.strip()
     if "://" not in raw:
         raw = "ws://" + raw
     u = urlparse(raw)
+    scheme = u.scheme.lower()
+    if scheme == "http":
+        scheme = "ws"
+    elif scheme == "https":
+        scheme = "wss"
+    if scheme in ("mqtt", "mqtts"):
+        if not allow_tcp:
+            raise ValueError("裸 TCP 需显式 use_tcp")
+        return urlunparse((scheme, u.netloc, u.path, u.params, u.query, u.fragment))
+    if scheme not in ("ws", "wss"):
+        raise ValueError(f"unsupported scheme {u.scheme}")
     path = u.path or ""
-    if not path.endswith("/mqtt"):
-        path = path.rstrip("/") + "/mqtt"
-    return urlunparse((u.scheme, u.netloc, path, u.params, u.query, u.fragment))
+    if path in ("", "/"):
+        path = "/mqtt"
+    return urlunparse((scheme, u.netloc, path, u.params, u.query, u.fragment))