feat(alerts): history reads as episodes; tests follow the confirm dialog (#5316, #5314)

History (#5316):
- Transitions fold into episodes (steward/alerts/episodes.py): each stretch
  out of quiet, the worst state it reached, how long it lasted, its worst
  reading against the rule ('3m 21s (fires above 3m)'), who was told across
  its changes, and its Ansible runs. The changes themselves fold under it.
- An episode cut by paging says so ('cleared later (above)', 'earlier').
- For one rule: a verdict ('Fired 4 times in the last 7d, 1h 2m in all') and
  no Rule column. Notified and Action show only when the range has any.

Tests:
- The confirm guard looks for a confirm( call, not the word in the comment
  that says it is gone (lesson #4365).
- The Hosts viewer test looks for the add-host dialog by id, since every page
  now carries the confirm dialog.

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

tests/integration/test_alert_history_page.py

@@ -68,14 +68,19 @@ def test_a_viewer_reads_the_alert_history(app):
         page = await resp.get_data(as_text=True)
         assert "Alert History" in page and 'href="/alerts/"' in page  # crumbs back to Alerts
         assert f"hot {tag}" in page and f"cold-note-{tag}" in page and f"old-{tag}" not in page
-        assert "CPU 98%" in page and "fires when CPU > 90%" in page
+        # One episode per stretch out of quiet (#5316): its worst reading against
+        # the rule, who was told across its changes, the changes folded under it.
+        assert '98% <span class="tone-dim">(fires above 90%)</span>' in page
         assert "email failed" in page and f"mx-{tag}: timed out" in page and "webhook sent" in page
-        assert f"muted · patch-{tag}" in page and "No CPU reading" in page
+        assert f"muted · patch-{tag}" in page and "No CPU reading" in page and "2 changes of state" in page
+        assert "<th>Rule</th>" in page and "<th>Notified</th>" in page and "<th>Action</th>" not in page
 
         resp = await client.get(f"/alerts/history?range=24h&rule={hot_id}", headers={"HX-Request": "true"})
         rows = await resp.get_data(as_text=True)
         assert "<html" not in rows and "<table" in rows
         assert f"old-{tag}" in rows and f"cold-note-{tag}" not in rows
+        assert "<th>Rule</th>" not in rows                                   # one rule: no column for it
+        assert "Fired 1 time</strong> in the last 24h" in rows                # its verdict
 
         # The next page as the reader scrolls: only older rows, without the table
         # around them, and the list says where it ends (#5211).
@@ -84,7 +89,8 @@ def test_a_viewer_reads_the_alert_history(app):
             "range": "24h", "rule": hot_id, "before": cursor(now - timedelta(minutes=3), "")})
         older = await resp.get_data(as_text=True)
         assert resp.status_code == 200 and "<table" not in older
-        assert "CPU 98%" in older and f"old-{tag}" in older and f"patch-{tag}" not in older
+        assert "98%" in older and f"old-{tag}" in older and f"patch-{tag}" not in older
+        assert "cleared later (above)" in older                              # its end is on the newer page
         assert "End of the list." in older and "data-scroll-more" not in older
 
         # The rules list links each rule to its history.