fix: select existing tenants by name in the operator portal

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a07ff8-19d0-7820-b4d0-1353833cb7fc

tests/test_postgres_store_adapter.py

@@ -158,6 +158,13 @@ class _FakePostgresCursor:
             self._rows = sorted(counts.items())
             return
 
+        if normalized.startswith("select distinct tenant"):
+            self._rows = [(tenant,) for tenant in sorted({
+                record.tenant for (record_type, _), record in self.connection.records.items()
+                if record_type == values[0] and record.tenant is not None
+            })]
+            return
+
         record_type = values[0]
         filter_columns = [
             column