feat: show IOL-style interface names on iol-runner ports

Name ports after the IOL interface they map to (Ethernet0/0, one 4-port
unit per adapter range) via the _get_container_ifname override point, so
the GNS3 UI matches the IOS CLI. Display only — the flat adapter number
remains the socket index.

tests/compute/docker/test_iol_docker_vm.py

@@ -177,6 +177,20 @@ def test_iol_memory_knob(compute_project, manager):
     assert vm._iol_memory == 2048
 
 
+# ---------------------------------------------------------------------------
+# Port naming
+# ---------------------------------------------------------------------------
+
+def test_ports_are_named_after_iol_interfaces(compute_project, manager):
+
+    vm = _make_vm(compute_project, manager, adapters=8)
+    assert vm._get_container_ifname(0) == "Ethernet0/0"
+    assert vm._get_container_ifname(3) == "Ethernet0/3"
+    # the second 4-port unit starts its own slot numbering
+    assert vm._get_container_ifname(4) == "Ethernet1/0"
+    assert vm._get_container_ifname(7) == "Ethernet1/3"
+
+
 # ---------------------------------------------------------------------------
 # create()
 # ---------------------------------------------------------------------------