refactor(backend): add list_running() to VmBackend seam (W1)

operations.vms.list_live_vms needs a backend-agnostic running-VM list for the web dashboard; is_running now shares the single vmrun-list parse.

tests/python/test_backends_protocol.py

@@ -52,3 +52,4 @@ def test_protocol_stubs_are_callable() -> None:
     assert b.get_ip(h) is None                                      # line 69
     assert b.list_snapshots(h) is None                              # line 73
     assert b.is_running(h) is None                                  # line 81
+    assert b.list_running() is None                                 # list_running stub

tests/python/test_workstation_backend.py

@@ -164,6 +164,36 @@ def test_is_running_returns_false_when_absent(
     assert backend.is_running(VmHandle(str(vmx))) is False
 
 
+# ── list_running ─────────────────────────────────────────────────────────────
+
+def test_list_running_parses_paths_and_skips_noise(
+    monkeypatch: pytest.MonkeyPatch, fake_vmrun: str
+) -> None:
+    """Header and ``Error:`` lines are dropped; each VMX becomes a handle."""
+    stdout = (
+        "Total running VMs: 2\n"
+        "/var/lib/ci/build-vms/Clone_a/Clone_a.vmx\n"
+        "Error: The VMware Tools are not running\n"
+        "/var/lib/ci/build-vms/Clone_b/Clone_b.vmx\n"
+    )
+    monkeypatch.setattr(subprocess, "run", lambda *a, **kw: _make_completed(0, stdout=stdout))
+    backend = WorkstationVmrunBackend(vmrun_path=fake_vmrun)
+    handles = backend.list_running()
+    assert [h.identifier for h in handles] == [
+        "/var/lib/ci/build-vms/Clone_a/Clone_a.vmx",
+        "/var/lib/ci/build-vms/Clone_b/Clone_b.vmx",
+    ]
+    assert [h.name for h in handles] == ["Clone_a", "Clone_b"]
+
+
+def test_list_running_returns_empty_on_failure(
+    monkeypatch: pytest.MonkeyPatch, fake_vmrun: str
+) -> None:
+    monkeypatch.setattr(subprocess, "run", lambda *a, **kw: _make_completed(1, stderr="boom"))
+    backend = WorkstationVmrunBackend(vmrun_path=fake_vmrun)
+    assert backend.list_running() == []
+
+
 # ── _resolve_vmrun(explicit=None) paths ───────────────────────────────────────
 
 def test_resolve_vmrun_uses_which(monkeypatch: pytest.MonkeyPatch, fake_vmrun: str) -> None: