feat(hosts): a host's health tiles span the card and the gaps match; Add host is a dialog on the list (#5290, #5291)

#5290 "Host page: the health tiles span the card's width; even spacing above Ansible":
the four tiles take equal quarters (halves on a phone) and their sparklines stretch
across them; the Monitors + Agent row drops the Agent card's own margin, so the gap
above Ansible is 1rem like every other.

#5291 "Add host opens as a dialog over the Hosts list": a native <dialog> on /hosts/,
opened by Add host or /hosts/?add=1. A name clash re-renders the list with it open,
the error and what was typed. GET /hosts/new is gone; hosts/form.html is Edit only.

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

tests/core/test_status.py

@@ -69,3 +69,12 @@ def test_sparkline_svg_handles_edge_cases():
     assert "polyline" in sparkline_svg([1, 2, 3])
     assert "polyline" in sparkline_svg([4, 4, 4])      # flat series, no div-by-zero
     assert "polyline" in sparkline_svg([1, None, 3])   # None values filtered
+
+
+def test_a_sparkline_can_stretch_across_its_tile():
+    """#5290: the host page's tiles are wide; the line fills them, stroke kept."""
+    wide = sparkline_svg([1, 2, 3], height=24, fill_width=True)
+    assert 'width="100%"' in wide and 'preserveAspectRatio="none"' in wide
+    assert 'vector-effect="non-scaling-stroke"' in wide
+    fixed = sparkline_svg([1, 2, 3])
+    assert 'width="80"' in fixed and "preserveAspectRatio" not in fixed