Split last_upsert (persisted write) and last_refresh (run liveness) in stats

tests/test_stats.py

@@ -96,6 +96,15 @@ def test_stats_no_error_by_default(source_engine, patched_cache):
     engine.close()
 
 
+def test_stats_exposes_last_upsert_and_last_refresh(source_engine, patched_cache):
+    engine = CachingEngine(source_engine)
+    engine.execute("SELECT id, name FROM products")
+    s = engine.stats.tables["products"]
+    assert s.last_upsert is not None   # the load wrote rows (persisted)
+    assert s.last_refresh is not None  # the load also counts as a refresh-cycle run
+    engine.close()
+
+
 # --- a table being loaded for the first time shows up as "loading" ----------