feat: Python/Java SDK 接入清单与打包文档

对真实 nixmsg 跑 DEVELOPMENT 第 9 节接入清单（跳过仅 JS 跨域），补 README/示例，并修 Paho/HiveMQ 真机联调死锁与鉴权分类。

sdk/python/examples/minimal.py

@@ -0,0 +1,31 @@
+"""最小示例：连接、收发、关闭。
+
+用法（需本地已启动 nixmsg，并开放注册或已有端）：
+  python examples/minimal.py ws://127.0.0.1:PORT/mqtt device-1 password12 peer-id
+"""
+
+from __future__ import annotations
+
+import sys
+import time
+
+from nixmsg import Body, Client, SendOptions, Target
+
+
+def main() -> None:
+    if len(sys.argv) < 5:
+        print(__doc__)
+        raise SystemExit(2)
+    url, eid, password, peer = sys.argv[1:5]
+    c = Client()
+    c.on_session(lambda token: print("session", token[:16] + "..."))
+    c.on_message(lambda msg: print("msg", msg.from_id, msg.id, msg.body.data))
+    c.on_connection(lambda ev: print("conn", ev.state.value, ev.reason))
+    c.connect(url, eid, password=password)
+    c.send(Target(kind="endpoint", id=peer), Body(data="hello from python"), SendOptions(delay_ms=0))
+    time.sleep(2)
+    c.close()
+
+
+if __name__ == "__main__":
+    main()