v0.2.1

Patch release. Nothing was removed and no exported signature changed.

iroh.ConnStats gained PTOs and SpuriousLosses. Adding fields to an exported struct breaks unkeyed composite literals; keyed literals are unaffected.

• A wildcard-bound endpoint now replies from the address a peer's datagrams arrived at, not whichever address the route picks. They differ on a multi-homed host or behind a bridge or container network, where a QUIC peer receiving packets from an address it never dialed fails path validation.
• Connect starts a handshake per dial target 250 ms apart and takes the first that completes, instead of walking them in turn. Unreachable direct addresses no longer cost a handshake timeout each before the relay path is tried.
• Path selection re-runs once a hole punch succeeds. A relay-to-direct upgrade that took about five seconds now takes tens of milliseconds.

On Linux the receive path uses UDP_GRO. Nothing changes on the wire, and other platforms keep the per-packet loop.

Three loss-recovery fixes in the vendored internal/qng, each a case where a connection could stall on a timer that was never set. golang.org/x/crypto moved to v0.56.0, clearing three unreachable govulncheck advisories.

See COMPATIBILITY.md for the full detail.