fix: filter out own outgoing frames on Windows client

Npcap in promiscuous mode loops back our own sent frames to the
capture callback. Without filtering, every DATA frame the client
sent was also processed as an incoming frame, duplicating the data
stream. This corrupted SSH sessions (Bad packet length 0x5353482D
= 'SSH-' — the version banner received twice).

Fix: compare source MAC in captured frames against our own MAC and
skip matches. Mirrors the PACKET_OUTGOING check on the Rust side.

win/gatuna-client/TunnelLink.cs

@@ -50,6 +50,11 @@ sealed class TunnelLink : IDisposable
         var et = (ushort)(data[12] << 8 | data[13]);
         if (et != Proto.EtherType)
             return;
+        // Skip our own outgoing frames (Npcap loops them back in promiscuous mode).
+        if (data[6] == _ourMac[0] && data[7] == _ourMac[1]
+            && data[8] == _ourMac[2] && data[9] == _ourMac[3]
+            && data[10] == _ourMac[4] && data[11] == _ourMac[5])
+            return;
         var srcMac = new byte[6];
         Buffer.BlockCopy(data, 6, srcMac, 0, 6);
         var payload = data.AsSpan(Proto.EthHeaderLen);