fix(identify): complete Identify on relayed connections to allow DCUtR initiation

[SilverFire]

Summary

In BasicHost.newStream and IdentifyService._NetNotifiee.connected, Identify was explicitly skipped for circuit-relay connections (conn.state.transport == 'circuit-relay').

Problem

Reference libp2p implementations (e.g. go-libp2p v0.47.0 holepuncher.go) require IdentifyWait(conn) to complete on inbound relayed connections before calling DirectConnect(remotePeer).

Because Dart skipped Identify on relayed connections:

1. When a Dart peer connected to a Go gateway via relay, Identify was never executed.
2. Go's IdentifyWait never completed for the relayed connection.
3. Go never learned Dart's supported protocols (such as /libp2p/dcutr) or Dart's observed addresses.
4. Go never triggered DCUtR hole punching (DirectConnect).

In addition:

• identifyWait contained a control-flow bug where alreadyIdentified / connClosed exited _connsMutex.synchronized early without setting completerToAwait, emitting false [IDENTIFY-WAIT-NO-COMPLETER] warning logs on reused connections.
• _NetNotifiee.disconnected removed connections from _conns without completing pending identifyWaitCompleter instances with an error on connection drop, leaving callers hanging.

Proposed Fix

• Remove the isRelayConn skip in BasicHost.newStream and IdentifyService._NetNotifiee.connected.
• Fix identifyWait control flow to return cleanly when already identified or closed.
• Reject pending identifyWaitCompleter instances with StateError on connection disconnect.
• Add deterministic Dart↔Go interop test verifying relayed Identify completion and automatic Go-initiated /libp2p/dcutr stream creation.