feat(quic-interop): scaffold quic-interop-runner endpoint module

Adds :quic-interop, a JVM-only module at quic/interop/ that implements
the quic-interop-runner Docker contract so we can drive matrix tests
against aioquic / quiche / picoquic / msquic / ngtcp2 / etc. as a
bug-finding harness.

Phase 0 supports only the `handshake` testcase; everything else returns
127 so the runner skips rather than fails. SSLKEYLOGFILE / QLOGDIR
plumbing is deferred to Phase 1.

https://claude.ai/code/session_01HcvfQq1ttPV9PkRoJb4nyT

settings.gradle

@@ -40,3 +40,5 @@ include ':quic'
 include ':nestsClient'
 include ':desktopApp'
 include ':cli'
+include ':quic-interop'
+project(':quic-interop').projectDir = file('quic/interop')