test(dashboard): count Hosts header cells, not bare <th> tags (#5214)

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

tests/core/test_dashboard_defaults.py

@@ -1,5 +1,6 @@
 """The dashboard starts from a curated layout, the duplicate widgets are gone,
 and the Overview says what each number counts (#5213)."""
+import re
 from datetime import datetime, timedelta, timezone
 from types import SimpleNamespace
 
@@ -127,7 +128,7 @@ async def test_the_hosts_widget_gives_a_verdict_and_load_against_cores(app):
     assert page.index("VDNT-Util01") < page.index("VDNT-Docker02")
     assert "16.8 / 8 cores" in page and "0.9 / 4 cores" in page
     assert "agent last reported" in page
-    assert page.count("<th>") == 5 and ">ping<" not in page and "24h" not in page
+    assert len(re.findall(r"<th[ >]", page)) == 5 and ">ping<" not in page and "24h" not in page
     assert not hex_colours(page), hex_colours(page)