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_structured.py

@@ -193,7 +193,14 @@ class TestSamplingSnapshotInvariant:
         terminal = ScriptedTerminal(["not json at all", '{"answer": 1, "reason": "r"}'])
         mw = _mw(strategy=NativeSchemaStrategy(), max_retries=1)
         await mw(
-            ChatRequest(messages=_MSGS, structured=Verdict, sampling=caller_sampling),
+            # overlay 与 sampling 传**同一个对象**,复现 client.py 的别名关系
+            # ——否则中间件就地改写 overlay 时不会波及 sampling,这条执法就是空的
+            ChatRequest(
+                messages=_MSGS,
+                structured=Verdict,
+                overlay=caller_sampling,
+                sampling=caller_sampling,
+            ),
             terminal,
         )
         assert len(terminal.requests) == 2  # 确实重问过
@@ -205,11 +212,20 @@ class TestSamplingSnapshotInvariant:
             assert "response_format" not in seen.sampling
 
     async def test_middleware_does_not_mutate_caller_mapping(self):
-        """决策 E 的第二条约束: 中间件只能 replace 派生,不得就地改这两个 dict。"""
+        """决策 E 的第二条约束: 中间件只能 replace 派生,不得就地改这两个 dict。
+
+        同样传同一对象: 生产中 overlay 与 sampling 是别名,任何对 overlay 的
+        就地改写都会同步毒化缓存 key 与遥测列。
+        """
         caller_sampling = {"seed": 7}
         terminal = ScriptedTerminal(['{"answer": 1, "reason": "r"}'])
         await _mw(strategy=NativeSchemaStrategy())(
-            ChatRequest(messages=_MSGS, structured=Verdict, sampling=caller_sampling),
+            ChatRequest(
+                messages=_MSGS,
+                structured=Verdict,
+                overlay=caller_sampling,
+                sampling=caller_sampling,
+            ),
             terminal,
         )
         assert caller_sampling == {"seed": 7}  # 调用方的对象未被污染