TCP client link

socket::TcpClientLink is a reconnecting TCP stream driven from loop(). The header is esphome/components/socket/tcp_client_link.h. It is compiled only when a component calls socket.require_tcp_client_link() from to_code; socket.require_tcp_listener() implies it.

The link owns the socket, the DNS lookup, the retry backoff and a 1 KiB outgoing buffer. A fatal read or write error closes the link, logs it and schedules the next attempt; the caller sees the edge through connected() and clears its own state there.

• begin(tag) from setup(); set_host, set_port and set_reconnect_interval from codegen setters.
• poll() once per loop while acting as a client. It is an inline no-op while connected or backing off.
• adopt(sock) takes over an accepted socket; the TCP listener is the usual caller.
• read(buf, len) returns bytes, 0 when nothing can move now, and -1 when the link dropped.
• queue(data, len) copies into the outgoing buffer and returns how many bytes fit; tx_tail() and tx_commit(n) give a zero copy fill bounded by tx_free(); flush_tx() sends the front and returns true once the buffer is empty.
• close() from on_shutdown(); it also clears the buffer, so bytes never leak into the next session.

consume_role_sockets(component) in socket/__init__.py does the socket accounting for a role keyed schema: one stream socket always, plus one listen socket when role is server.

uart_tcp is the first caller; tcp_uart follows in esphome#20026.