fix(listener): stop dropping a peer's streams that arrive during connection setup

ListenerQUIC installed only a no-op bootstrap connection callback in the
NEW_CONNECTION handler and deferred the real ClientQUIC callback to the
ThreadPool, alongside per-connection onConnect setup. An HTTP/3 peer (notably
Chromium) opens its control + QPACK + request streams the instant the QUIC
handshake completes — potentially before that deferred task ran. Those early
PEER_STREAM_STARTED events were delivered to the bootstrap and silently
dropped, so the session never completed. Over the network this surfaced as an
intermittent "WebTransport connection rejected" that cleared on retry.

Construct the ClientQUIC (and thus install its real connection callback)
synchronously inside NEW_CONNECTION, before the handler returns and before
msquic delivers any further events. pendingAccepted now holds the constructed
ClientQUIC*; the accept loops just dispatch it, and the destructor cleans up
any peer accepted but never dispatched.

Also park WT data streams that arrive before their CONNECT session is
registered (the stream demux races the CONNECT handler) and drain them on
registration, instead of dropping them.

Tests:
- New ShouldNotDropEarlyStreams reproduces the race deterministically by
  saturating the ThreadPool so onConnect is gated while the client opens its
  request stream; fails on the pre-fix build, passes after.
- Give ShouldEchoWebTransport its own port (8085) so it no longer collides
  with ShouldSendRecieveKeepaliveHTTP (8083) under the parallel test runner.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

project.cpp

@@ -111,6 +111,7 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
     // crafter-network static lib via .Dependencies({ &cfg }).
     if (cfg.target == "x86_64-pc-linux-gnu") {
         cfg.AddTest("ShouldEchoWebTransport").Dependencies({ &cfg });
+        cfg.AddTest("ShouldNotDropEarlyStreams").Dependencies({ &cfg });
         cfg.AddTest("ShouldSend").Dependencies({ &cfg });
         cfg.AddTest("ShouldSendRecieveHTTP").Dependencies({ &cfg });
         cfg.AddTest("ShouldSendRecieveKeepaliveHTTP").Dependencies({ &cfg });