Show all dialogs and the guest table as titled boxes

The info screen's style now applies everywhere. The guest table sits
in a "Guests" frame with the active context in its bottom border.
Every dialog is a centred box with a title, labelled fields and the
buttons bottom right: confirm (titled by the action), edit resources,
switch context, back up and edit network.

Fixed:
- The network dialog hid most of its fields. In Horizontal rows
  Textual gave Select a width of 1 and Input 100 %, which pushed
  bridge, firewall, the IP mode selects and the gateways off-screen.
  Every field in a row now has an explicit width.
- A guest name or note containing markup, such as "a[/b]", crashed the
  guest table and the dialogs, because DataTable cells and border
  titles were parsed as markup. They are now plain text.

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

tests/test_app.py

@@ -1883,3 +1883,106 @@ async def test_info_has_separate_titled_backup_and_network_sections(fake):
             "unavailable",
             "addresses",
         }
+
+
+# --- boxed design: every dialog a titled box, main table in a titled frame ----------
+
+from textual.content import Content
+from textual.widgets import Label
+
+SIZE = (100, 40)
+
+
+def visible(app, widget):
+    r = widget.region
+    return (
+        r.width >= 3
+        and r.height >= 1
+        and r.right <= app.size.width
+        and r.bottom <= app.size.height
+    )
+
+
+def label_texts(screen):
+    return {str(w.render()).strip() for w in screen.query(Label)}
+
+
+async def test_net_screen_shows_every_field_inside_the_screen(fake):
+    # bug: in the old rows Select got width 1 and Input 100 %, pushing fields off-screen
+    fake.net_configs[100] = dict(CT_CONFIG)
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await open_net(app, pilot)
+        for wid in ("iface", "bridge", "tag", "firewall", "ipv4", "ipv4_cidr", "ipv4_gw",
+                    "ipv6", "ipv6_cidr", "ipv6_gw", "apply", "cancel"):  # fmt: skip
+            assert visible(app, app.screen.query_one(f"#{wid}")), wid
+
+
+async def test_net_screen_labels_and_ip_sections(fake):
+    fake.net_configs[100] = dict(CT_CONFIG)
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await open_net(app, pilot)
+        assert {"Interface", "Bridge", "VLAN"} <= label_texts(app.screen)
+        assert "IPv4" in str(app.screen.query_one("#ipv4_section").border_title)
+        assert "IPv6" in str(app.screen.query_one("#ipv6_section").border_title)
+
+
+async def test_edit_screen_fields_have_labels(fake):
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await open_edit(app, pilot)
+        assert {"Cores", "Memory (MiB)", "Disk", "Grow by (GiB)"} <= label_texts(
+            app.screen
+        )
+
+
+async def open_each_dialog(app, pilot):
+    """Yields after each dialog is open; closes it with escape afterwards."""
+    await settle(app, pilot)
+    for keys in (["S"], ["e"], ["c"], ["i", "b"], ["i", "n"]):
+        for k in keys:
+            await pilot.press(k)
+            await settle(app, pilot)
+        yield keys
+        for _ in keys:
+            await pilot.press("escape")
+            await settle(app, pilot)
+
+
+async def test_every_dialog_is_a_titled_centred_box(fake):
+    fake.net_configs[108] = dict(VM_CONFIG)
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        async for keys in open_each_dialog(app, pilot):
+            box = app.screen.query_one("#dialog")
+            assert str(box.border_title).strip(), keys
+            assert box.region.width < app.size.width, keys  # a box, not full screen
+            assert box.region.x > 0, keys  # centred
+
+
+async def test_main_table_is_framed_with_title_and_context(fake):
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await settle(app, pilot)
+        frame = app.query_one("#guests_section")
+        assert "Guests" in str(frame.border_title)
+        assert "mainframe" in str(frame.border_subtitle)
+
+
+@pytest.mark.parametrize("keys", [["e"], ["i", "b"], ["i", "n"]])
+async def test_guest_name_with_markup_characters_does_not_break_dialogs(fake, keys):
+    # border titles are parsed as markup; a name like "a[/b]" must be shown literally
+    fake.guests = [dict(VM, name="a[/b]")]
+    fake.net_configs[108] = dict(VM_CONFIG)
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await settle(app, pilot)
+        for k in keys:
+            await pilot.press(k)
+            await settle(app, pilot)
+        title = app.screen.query_one("#dialog").border_title
+        assert (
+            "a[/b]" in Content.from_markup(title).plain
+        )  # what is shown, not how it is stored
+        assert app.is_running