Add the task log: recent tasks with status, Enter shows the log

l on the main screen opens "Tasks", the recent cluster tasks newest
first. l on the info screen shows only that guest's tasks. Columns:
start, duration (or "running"), node, type, VMID ("-" for node
tasks), user and status. A failed task gets a "!" in the leading
column. Enter opens the task's log in a plain-text widget, so the
output is never parsed as markup.

`task list -o json` has no start or end times, so the list comes from
`/cluster/tasks`. The upid is validated (it must start with "UPID:")
before it goes in as a positional argument.

Review fixes:
- A finished task without a start time no longer crashes the app; its
  duration shows "-".
- "running" now means there is no endtime. A finished task with an
  empty status shows "unknown" and is flagged.

Read-only live check: 25 tasks listed, and the log of the newest
(vzdelsnapshot 104) ends with TASK OK.

Closes #10

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

tests/test_cli.py

@@ -1295,3 +1295,48 @@ def test_take_snapshot_refuses_description_that_looks_like_an_option(fake):
             {"vmid": 104, "node": "mainframe", "type": "lxc"}, "snap1", "-y"
         )
     assert fake.calls == []
+
+
+# --- issue #10: task log (spec: "Task log (issue #10)" > cli.py) ------------------------
+
+UPID = "UPID:mainframe:0001:00A:68F:qmstart:108:root@pam:"
+
+
+def test_tasks_argv_is_cluster_tasks_json(fake):  # tasks(): api get /cluster/tasks
+    fake.result = ("[]", "", 0)
+    assert cli.tasks() == []
+    assert fake.argv == ["cv4pve-cli", "api", "get", "/cluster/tasks", "-o", "json"]
+
+
+def test_tasks_newest_first_including_running_without_endtime(
+    fake,
+):  # tasks(): newest first
+    raw = [
+        {"upid": "a", "starttime": 100, "endtime": 150, "status": "OK"},
+        {"upid": "c", "starttime": 300},  # running: no endtime, no status
+        {"upid": "b", "starttime": 200, "endtime": None},
+    ]
+    fake.result = (json.dumps(raw), "", 0)
+    assert [t["upid"] for t in cli.tasks()] == ["c", "b", "a"]
+
+
+def test_tasks_failure_raises_clierror(monkeypatch):  # failure surfaces as CliError
+    FakeRun(monkeypatch, "Error: boom", returncode=1)
+    with pytest.raises(cli.CliError):
+        cli.tasks()
+
+
+def test_task_log_argv_and_returns_text(fake):  # task_log(): task log <upid>
+    fake.result = ("starting\nTASK OK\n", "", 0)
+    out = cli.task_log(UPID)
+    assert fake.argv == ["cv4pve-cli", "task", "log", UPID]
+    assert "TASK OK" in out
+
+
+@pytest.mark.parametrize("bad", ["-y", "--help", "", "108", "x UPID:a"])
+def test_task_log_rejects_non_upid_without_calling_subprocess(
+    fake, bad
+):  # ValueError unless UPID:
+    with pytest.raises(ValueError):
+        cli.task_log(bad)
+    assert fake.calls == []