Production Lightstreamer.Transport on Mint and Mint.WebSocket.

A small GenServer owns the Mint connection: connect/2 blocks until the WebSocket upgrade (subprotocol TLCP-2.5.0.lightstreamer.com) completes, then inbound text frames flow to the owner as {:transport, t, {:text, _}} messages. Frames may be fragmented or coalesced relative to server lines — the session's line buffering absorbs that. Pings are answered here; a close frame or transport error surfaces as {:transport, t, :closed}.