Add time-travel assertion to replace integration tests

The .append() before replace exists to produce a snapshot. The
existing assertion ('old snapshot id in metadata.snapshots') only
proves the metadata entry survived — not that it's actually
readable. Adding a scan(snapshot_id=old_snapshot_id) round-trip
proves the schema + manifest references for the pre-replace
snapshot are still resolvable through the real object store, not
just present in the metadata document.

Author: smaheshwar-pltr

tests/integration/test_catalog.py

@@ -907,6 +907,10 @@ def test_replace_table(test_catalog: Catalog, database_name: str, table_name: st
     assert replaced.metadata.table_uuid == original.metadata.table_uuid
     assert replaced.current_snapshot() is None
     assert any(s.snapshot_id == original_snapshot_id for s in replaced.metadata.snapshots)
+    # Time-travel back to the pre-replace snapshot returns the rows that were there before.
+    time_travel = replaced.scan(snapshot_id=original_snapshot_id).to_arrow()
+    assert time_travel.num_rows == 3
+    assert sorted(time_travel.column("id").to_pylist()) == [1, 2, 3]
 
 
 @pytest.mark.integration
@@ -935,3 +939,7 @@ def test_replace_table_transaction(test_catalog: Catalog, database_name: str, ta
     assert replaced.current_snapshot().snapshot_id != old_snapshot_id  # type: ignore[union-attr]
     assert any(s.snapshot_id == old_snapshot_id for s in replaced.metadata.snapshots)
     assert replaced.scan().to_arrow().num_rows == 2
+    # Time-travel back to the pre-replace snapshot returns the original row.
+    old_via_time_travel = replaced.scan(snapshot_id=old_snapshot_id).to_arrow()
+    assert old_via_time_travel.num_rows == 1
+    assert old_via_time_travel.column("id").to_pylist() == [1]