fix(g2-followup): tiebreak newest-first journal scans on event_id (#159)

The bounded journal scan added in S4 (PR #158) ordered by
`{time_column} DESC` with no secondary key, unlike the existing
ascending path's `ASC, event_id ASC` total order. Two rows sharing an
identical timestamp for the same entity resolved to whichever the
backend happened to emit first — nondeterministic across backends and
across reloads. Add `, event_id DESC` to restore a total order and
match the old last-write-wins tie behavior deterministically.

Found in an Opus review pass standing in for the unavailable Codex
review step.

Co-authored-by: JuliaEdom <uedomskikh@gmail.com>

Author: brownjuly2003-code

src/serving/semantic_layer/query/engine.py

@@ -222,7 +222,7 @@ def render(value: str) -> str:
             sql = f"{sql} WHERE {' AND '.join(where_clauses)}"
         order_column = time_column or "event_id"
         if newest_first:
-            sql = f"{sql} ORDER BY {order_column} DESC"
+            sql = f"{sql} ORDER BY {order_column} DESC, event_id DESC"
         else:
             sql = f"{sql} ORDER BY {order_column} ASC, event_id ASC"
         if limit is not None:

tests/unit/test_pipeline_events_scan.py

@@ -84,7 +84,7 @@ def test_family_filters_and_limit_are_static_sql() -> None:
     ((sql, _),) = backend.calls
     assert "topic = 'events.validated'" in sql
     assert "event_type IN ('click', 'page_view', 'add_to_cart')" in sql
-    assert sql.endswith("ORDER BY processed_at DESC LIMIT 10")
+    assert sql.endswith("ORDER BY processed_at DESC, event_id DESC LIMIT 10")
 
 
 def test_missing_journal_returns_empty_without_query() -> None: