fix: make the sampling invariant test actually enforce the constraint

The test passed overlay and sampling as separate objects while production
aliases them, so an in-place mutation slipped through it. Also syncs the
telemetry schema page and adds the missing postgres round-trip assertion.

tests/unit/test_ports.py

@@ -116,6 +116,7 @@ class _DummyRecorder:
         cost,
         cached_prompt_tokens,
         model_reported,
+        sampling,
     ) -> None: ...