Fix generate accurate session_uri for nested SSE paths

Author: sebin1213

src/mcp/server/sse.py

@@ -94,6 +94,7 @@ async def connect_sse(self, scope: Scope, receive: Receive, send: Send):
         read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
         write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
 
+        session_id = uuid4()
         request_path = scope["path"]
         match = re.match(r"^/([^/]+(?:/mcp)?)/sse$", request_path)
         mount_prefix = match.group(1) if match else ""