feat(core): TCP in the simulation core

engine.ts ports Swift's "Java-compatible TCP sockets" in one piece, since
half a state machine could not be checked: server and client sockets (a
free port from Java's random numbers on their own seed), the three-way
handshake with its result (connected, invalid socket, unreachable, timed
out), segments of 1460 bytes, messages up to the push, a timeout of
3 × 2.5 s with at most three attempts, closing through every Java state
including TIME_WAIT (2.5 s), sequence numbers modulo 2^32.

Three scenarios match the Swift engine trace for trace: a LAN with data
over three segments, closing from both ends, a closed port and an
unreachable host; two networks through a router with a firewall rule,
data lost until the connection closes, and an accepted socket that does
not hold the port of its closed listener; CLOSING, reached by a lost FIN.
The engine delivers a FIN within the same close, so both ends close at
once only with packet loss; an empty message does not arrive in Swift (it
does not advance the sequence number), nor here.

Swift's four TCP engine tests are ported, with tests for stopping, a
foreign SYN+ACK at a listener and the flag names. 17 mutation probes, 16
caught; the other (delivered, not waited, not connected gives unreachable)
cannot be reached through Swift's engine, which never sends a reset and
always acknowledges correctly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/test/scenarios/udp-lan.swift.json

@@ -84,30 +84,39 @@
       "localIp" : null,
       "localPort" : 51180,
       "node" : "00000000-0000-0000-0000-000000000102",
+      "parent" : null,
       "protocol" : "udp",
       "queued" : 0,
       "remoteIp" : "192.168.0.10",
-      "remotePort" : 5000
+      "remotePort" : 5000,
+      "session" : null,
+      "tcpState" : null
     },
     {
       "id" : "00000000-0000-0000-0000-000000000003",
       "localIp" : "192.168.0.30",
       "localPort" : 7000,
       "node" : "00000000-0000-0000-0000-000000000103",
+      "parent" : null,
       "protocol" : "udp",
       "queued" : 0,
       "remoteIp" : null,
-      "remotePort" : null
+      "remotePort" : null,
+      "session" : null,
+      "tcpState" : null
     },
     {
       "id" : "00000000-0000-0000-0000-000000000004",
       "localIp" : null,
       "localPort" : 5000,
       "node" : "00000000-0000-0000-0000-000000000101",
+      "parent" : null,
       "protocol" : "udp",
       "queued" : 0,
       "remoteIp" : null,
-      "remotePort" : null
+      "remotePort" : null,
+      "session" : null,
+      "tcpState" : null
     }
   ],
   "switchTables" : {