feat(settings): Settings → System shows table sizes and what the last cleanup removed (#5469)

#5469 "Settings → System: table sizes and what the last cleanup removed".

- Storage: each table's size on disk (pg_total_relation_size, indexes and TOAST
  included) and Postgres's row estimate (reltuples), largest first, the 15
  largest by name and the rest summed, under the database's total size. Read
  from the catalog only, never by counting rows.
- Last cleanup: when it ran, how long it took, and what each pass removed (each
  aged table, run log files, the metric and Docker rollups, the log ring), or
  "Nothing was past its window". run_cleanup now returns that summary and keeps
  it as the cleanup.last_run setting, as reports.last_sent_at does; cleanup_secs
  (#5467) is recorded from the same figure.
- A hint links to where each retention window is set.

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

tests/core/test_steward_health.py

@@ -8,6 +8,16 @@ from quart import render_template, session
 from steward.core import health
 
 AT = datetime(2026, 10, 9, 12, 0, tzinfo=timezone.utc)
+STORAGE = {"total": 3 * 2**30, "rest": {"count": 0, "bytes": 0},
+           "tables": [{"name": "plugin_metrics", "bytes": 2 * 2**30, "rows": 41_000_000},
+                      {"name": "docker_logs", "bytes": 512 * 2**20, "rows": None}]}
+
+
+async def _page(app, ctx, storage=STORAGE, cleanup=None):
+    async with app.test_request_context("/settings/system/"):
+        session["user_role"] = "admin"
+        page = await render_template("settings/system.html", **ctx, storage=storage, cleanup=cleanup)
+    return " ".join(page.split())
 
 
 def _previews(**over):
@@ -52,10 +62,50 @@ async def test_the_page_reads_as_a_verdict_then_each_measure(app, previews):
     got = await health.process_health(None)
     for r in got["rows"]:
         r["spark"] = ""
-    async with app.test_request_context("/settings/system/"):
-        session["user_role"] = "admin"
-        page = " ".join((await render_template("settings/system.html", **got)).split())
+    page = await _page(app, got)
     assert '<span class="tone-warn">Steward wasn&#39;t watching for up to 7m' in page
     assert 'title="<' not in page          # a <time> element never lands inside an attribute
     assert "Database round trip" in page and "4 ms" in page and "2 ms – 9 ms" in page
     assert page.index("page-verdict") < page.index("Agent posts per minute")
+
+
+# ── Storage and the last cleanup (#5469) ─────────────────────────────────────
+
+async def test_tables_largest_first_then_what_the_cleanup_removed(app, previews):
+    previews()
+    got = await health.process_health(None)
+    for r in got["rows"]:
+        r["spark"] = ""
+    cleanup = {"at": AT, "secs": 12.5, "passes": 14,
+               "removed": [("plugin_metrics: raw samples rolled into hourly", 86_400)]}
+    page = await _page(app, got, cleanup=cleanup)
+    assert "The database takes 3.0 GiB on disk." in page
+    assert page.index(">plugin_metrics<") < page.index(">docker_logs<")
+    assert "41,000,000" in page and "512.0 MiB" in page
+    assert "took 12s" in page and "86,400" in page
+    assert page.index("Steward itself") < page.index("Storage") < page.index("Last cleanup")
+
+
+async def test_a_quiet_cleanup_and_one_not_yet_run_each_say_so(app, previews):
+    previews()
+    got = await health.process_health(None)
+    for r in got["rows"]:
+        r["spark"] = ""
+    quiet = await _page(app, got, cleanup={"at": AT, "secs": 1.0, "passes": 14, "removed": []})
+    assert "Nothing was past its window (14 passes)." in quiet
+    assert "None has finished since this version started" in await _page(app, got)
+
+
+async def test_the_last_cleanup_keeps_only_what_went(monkeypatch):
+    stored = {"at": "2026-10-09T12:00:00+00:00", "secs": 3.2,
+              "removed": [["audit_events: older than 365 days", 0], ["docker_logs: past the age window", 7]]}
+
+    async def fake(db, key):
+        assert key == "cleanup.last_run"
+        return stored
+    monkeypatch.setattr("steward.core.settings.get_setting", fake)
+    got = await health.last_cleanup(None)
+    assert got["at"] == AT and got["passes"] == 2
+    assert got["removed"] == [("docker_logs: past the age window", 7)]
+    stored = {}
+    assert await health.last_cleanup(None) is None