run.sh: add a net mode (skip + tablet + networkprovider taptun) for the crash-work configuration

harness/mame/run.sh

@@ -8,6 +8,8 @@
 #   ./run.sh headless [N]    no window; dump frame N (default 600) into this directory
 #   ./run.sh stub            faithful, plus an opt-in stand-in for the level-0
 #                            keyboard-port test fixture -> reaches level 1
+#   ./run.sh net             skip + tablet + the LANCE attached to a host tap
+#                            (networkprovider taptun): the crash-work configuration
 #   ./run.sh mouse           skip + VSXXX-AA mouse: the *faithful* pointing device.
 #                            The tablet is the default; this sets VT1200_MOUSE=1
 #   ./run.sh <mode> -- <extra MAME options>
@@ -86,6 +88,17 @@ case "$MODE" in
             "$MAME" vt1200 "${COMMON[@]}" -window "$@"
         ;;
 
+    net)
+        # the crash-work configuration: skip + tablet (already the default) + the
+        # LANCE attached to a host tap, so frames actually leave the machine.  The
+        # driver needs nothing -- MAME's am79c90 brings its own network interface
+        # (device_network_interface); the OSD provider is the only missing link.
+        # Requires the tap to exist and be owned by your user; see the README's
+        # "host-side network plumbing" plan for the sequence.
+        exec env VT1200_SKIP_LEVEL1=1 \
+            "$MAME" vt1200 "${COMMON[@]}" -networkprovider taptun -window "$@"
+        ;;
+
     mouse)
         # force the faithful VSXXX-AA mouse.  The tablet is the default (absolute
         # pointing), so this is the opt-out.  Both need the lightgun options in COMMON