feat: carry the per-call tier down to the transport that must send it

The Transport port took the request apart into five arguments, so a tier
placed on ChatRequest could never reach _build_payload: the field was set,
read by nobody, and silently ignored - the exact shape of failure that sent
downstream to extra_body in the first place.

complete() now takes reasoning_effort with no default, matching the
TelemetryRecorder convention: a default would turn a missing hand-off into
a silent 'no opinion'. All four fakes move with it, since @runtime_checkable
checks method names and not signatures.

EmbeddingTransport and OcrTransport are deliberately left alone - they have
no reasoning semantics - and a test now holds that line.

_build_payload drops its inline sugar conversion for effective_effort(), so
the guard and the hot path share one judgement, and passes the source's
effort_fallback for the same reason.

src/polygateway/ports.py

@@ -12,6 +12,7 @@ from typing import Any, Protocol, runtime_checkable
 
 from .types import (
     ChatRequest,
+    Effort,
     EmbeddingTransportResult,
     LLMResponse,
     OcrLayoutResult,
@@ -36,7 +37,16 @@ class Middleware(Protocol):
 
 @runtime_checkable
 class Transport(Protocol):
-    """一次原始调用的协议细节(请求组装/流式解析/错误翻译);不含任何治理。"""
+    """一次原始调用的协议细节(请求组装/流式解析/错误翻译);不含任何治理。
+
+    `reasoning_effort` 是本次调用要求的推理档位(`None` = 不表态,随源级配置)。
+    它必须走**协议参数**而不能让 transport 自己去读 `ChatRequest`: 端口只收拆开的
+    请求要素,是为了让 transport 不依赖洋葱内部的请求类型(P7 端口最内层)。
+
+    该参数**不设默认值**,与 `TelemetryRecorder.record_llm_call` 同一既有约定:
+    库外无第三方实现者,写全签名的成本为零,而默认值会把"某一层漏传"变成静默的
+    "调用方没表态"——一次本该报错的漏配就此变成一次悄悄涨价的调用。
+    """
 
     async def complete(
         self,
@@ -46,6 +56,7 @@ class Transport(Protocol):
         stream: bool,
         overlay: dict[str, Any],
         call_id: str,
+        reasoning_effort: Effort | None,
     ) -> TransportResult: ...