IPv6 socket host and peer queries return an IPv4 address instead of the endpoint #218

IPv6 TCP connections work, but querying their local and remote endpoints returns an IPv4-looking 0.0.0.0 instead of the actual IPv6 address.

Regression coverage first: test/regression/SocketIpv6Endpoint, using the existing regression layout. Bind a listener to ::1 with an ephemeral port, connect a client to that port, accept it, and check listener.host(), client.host(), client.peer() and accepted.peer(). All four addresses should be ::1. Add an explicit IPv6 availability check for platforms without IPv6 loopback in CI.

Confirmed on Linux x86_64 with Haxe 4.3.3:

listener address: 0.0.0.0
client local address: 0.0.0.0
client peer address: 0.0.0.0
server peer address: 0.0.0.0

The connection itself succeeds. In src/hx/libs/std/Socket.cpp, socket_host, socket_peer and socket_accept use sockaddr_in even for AF_INET6 sockets. host/peer interpret the returned IPv6 structure as an IPv4 structure. The location interpreted as the IPv4 address is the IPv6 flow-info field, not the IPv6 address. accept discards the truncated address, so it still creates a usable accepted socket.

Use sockaddr_storage or family-appropriate structures and preserve the address family, full address and relevant IPv6 scope information. The legacy host/peer ABI returns only two Int values, so fixing the public Host result needs an additive native interface and a coordinated Haxe cpp standard-library change. Its current wrapper always constructs an IPv4 Host from that integer result.

Check that ports still round-trip correctly, cover IPv4 as a control, and add scoped-address coverage where available. Do not silently reinterpret an unsupported address family as IPv4.

No runtime implementation changes are included.