Edit autostart, startup order and tags from the info screen

The info screen's Resources table shows Autostart (yes/no), Startup
(order, up and down delays) and Tags. o opens a dialog to change them.
Only keys that differ are sent, in one `set <kind> config` call
through the existing set_net. A confirm lists the old and new value
of each key.

Tags are removed with `--delete tags` on set config. The CLI also has
a `delete ct|vm ... tags` command, but it shares the form that
destroys the whole guest, so the app never uses it; nothing in the
code builds a delete ct|vm argv. Inputs are validated before sending:
startup values must be ints >= 0, and tags must match
[A-Za-z0-9_][A-Za-z0-9_+.-]*. They are split on ; , or whitespace and
deduplicated.

Live test on CT 104: onboot 1 -> 0, startup order=5,up=10, tag
tui-test added, then all set back through the dialog. The config
ended identical to the baseline.

Closes #18

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

tests/test_cli.py

@@ -1388,3 +1388,119 @@ def test_version_argv_and_strips(fake):
 
 def test_tested_version_constant():
     assert cli.TESTED_VERSION == "2.4.0"
+
+
+# --- #18: startup order and tags (spec: "Autostart, startup order and tags") ----------
+
+
+@pytest.mark.parametrize(
+    ("args", "expected"),
+    [
+        ((2, 10, 30), "order=2,up=10,down=30"),
+        ((2, 10, None), "order=2,up=10"),
+        ((2, None, None), "order=2"),
+        ((None, 10, None), "up=10"),
+        ((None, None, 30), "down=30"),
+        ((None, 10, 30), "up=10,down=30"),
+        ((0, 0, 0), "order=0,up=0,down=0"),  # 0 is a value, not "unset"
+        ((None, None, None), None),
+    ],
+)
+def test_startup_value_builds_only_the_given_parts(args, expected):
+    assert cli.startup_value(*args) == expected
+
+
+@pytest.mark.parametrize(
+    "args", [(-1, None, None), (None, -5, None), (None, None, -30), (1, 2, -1)]
+)
+def test_startup_value_rejects_negatives(args):
+    with pytest.raises(ValueError):
+        cli.startup_value(*args)
+
+
+@pytest.mark.parametrize("bad", ["x", 1.5, [1]])
+def test_startup_value_rejects_non_ints(bad):
+    for args in ((bad, None, None), (None, bad, None), (None, None, bad)):
+        with pytest.raises(ValueError):
+            cli.startup_value(*args)
+
+
+@pytest.mark.parametrize(
+    ("text", "expected"),
+    [
+        ("order=2,up=10,down=30", (2, 10, 30)),
+        ("3", (3, None, None)),  # a bare leading number is the order
+        ("up=5", (None, 5, None)),
+        ("order=2,up=10", (2, 10, None)),
+        ("3,up=5", (3, 5, None)),
+        ("down=7", (None, None, 7)),
+        (None, (None, None, None)),
+        ("", (None, None, None)),
+    ],
+)
+def test_parse_startup(text, expected):
+    assert cli.parse_startup(text) == expected
+
+
+@given(
+    st.tuples(*[st.one_of(st.none(), st.integers(min_value=0, max_value=10**6))] * 3)
+)
+def test_parse_startup_inverts_startup_value_property(parts):
+    assert cli.parse_startup(cli.startup_value(*parts)) == parts
+
+
+@pytest.mark.parametrize(
+    ("text", "expected"),
+    [
+        ("os", "os"),
+        ("a;b;c", "a;b;c"),
+        ("a,b", "a;b"),
+        ("a b", "a;b"),  # whitespace separates: two tags, not one with a space
+        ("a;b, c  d", "a;b;c;d"),
+        ("a; b; c", "a;b;c"),
+        ("a;b;a;c;b", "a;b;c"),  # duplicates dropped, first occurrence wins
+        ("c;a;b", "c;a;b"),  # order kept, not sorted
+        (";;a;;,, b;", "a;b"),  # empties dropped
+        ("172.16.41.200", "172.16.41.200"),  # IP-like tag is valid
+        ("172.16.41.200;community-script;os", "172.16.41.200;community-script;os"),
+        ("_x;a+b;a.b;a-b;9", "_x;a+b;a.b;a-b;9"),
+    ],
+)
+def test_tags_value_normalises(text, expected):
+    assert cli.tags_value(text) == expected
+
+
+@pytest.mark.parametrize("text", ["", " ", ";", " ; , ;", "\n\t"])
+def test_tags_value_empty_is_none(text):
+    assert cli.tags_value(text) is None
+
+
+@pytest.mark.parametrize(
+    "bad", ["-x", "a;b!", "!", "a;-b", ".a", "+a", "a/b", "a;b@c", "ä"]
+)
+def test_tags_value_rejects_invalid_tags(bad):
+    with pytest.raises(ValueError):
+        cli.tags_value(bad)
+
+
+_TAG = st.from_regex(r"[A-Za-z0-9_][A-Za-z0-9_+.-]*", fullmatch=True)
+_SEP = st.sampled_from([";", ",", " ", "; ", ", ", "  ", ";;"])
+
+
+@st.composite
+def _valid_tag_text(draw):
+    tags = draw(st.lists(_TAG, max_size=6))
+    out = ""
+    for tag in tags:
+        out += tag + draw(_SEP)
+    return out
+
+
+@given(_valid_tag_text())
+def test_tags_value_is_idempotent_property(text):
+    once = cli.tags_value(text)
+    if once is None:
+        assert text.replace(";", "").replace(",", "").strip() == ""
+    else:
+        assert cli.tags_value(once) == once
+        assert len(set(once.split(";"))) == len(once.split(";"))  # no duplicates