Implement QUIC networking for wrsrvd (server) and wrclient (client) using
quinn over rustls with self-signed certificates. Three logical channels:
control (bidirectional), display (server->client unidirectional), and
input (client->server unidirectional).
Server runs tokio in a background thread, communicating with the compositor
via std::sync::mpsc channels. Client exposes an async connect() API that
returns a ServerConnection with methods for sending input and receiving
frames.
Key design note: quinn streams are lazily materialized -- accept_bi/
accept_uni on the peer won't resolve until data is written. The handshake
protocol accounts for this by having each side write immediately after
opening streams.
