Rewrite ws_client.py against the documented WebSocket API

Replaces the previous order-book/account-only client with a full
implementation of the channels documented at
https://apidocs.lighter.xyz/docs/websocket-reference.

The new WsClient supports every documented channel (order book,
ticker, market_stats, spot_market_stats, trade, candle, all
account_* streams, user_stats, notification, pool_data, pool_info,
height) plus jsonapi/sendtx and jsonapi/sendtxbatch transaction
submission. It keeps the existing public surface used in
examples/ws.py and examples/ws_async.py (order_book_ids,
account_ids, on_order_book_update, on_account_update, run(),
run_async()) and adds add_* helpers, async subscribe/unsubscribe,
send_tx/send_tx_batch, readonly mode, ping/pong handling,
configurable WebSocket keepalive, and optional auto-reconnect.

Author: devin-ai-integration[bot]