feat: strip extra_body on the embedding and OCR paths with a warning

Stripping is load-bearing, not tidying: those transports never send the
value, so leaving it would make telemetry record a parameter never sent.

src/polygateway/embedding.py

@@ -41,7 +41,12 @@ from polygateway.middleware.ratelimit import QuotaGate
 from polygateway.middleware.retry import _failure_reason, backoff_delay
 from polygateway.middleware.telemetry import TelemetryEmitter
 from polygateway.sources import SourceCooldownMemo
-from polygateway.types import ChatRequest, EmbeddingResponse, LLMResponse
+from polygateway.types import (
+    ChatRequest,
+    EmbeddingResponse,
+    LLMResponse,
+    strip_unsupported_extra_body,
+)
 
 if TYPE_CHECKING:
     from collections.abc import Awaitable, Callable, Mapping
@@ -111,7 +116,9 @@ class EmbeddingClient:
         if expected_dim is not None and expected_dim < 1:
             raise ValueError("expected_dim 必须 ≥ 1")
         self._scope = scope
-        self._sources = list(sources)
+        # embed payload 硬编码 {model, input},带 extra_body 的源必须先剥离,
+        # 否则遥测会记录一个从未发出的采样参数(issue #4 决策 G)
+        self._sources = strip_unsupported_extra_body(list(sources), path="embedding")
         self._selector = selector
         self._quota = QuotaGate(limiter)
         self._breaker = BreakerGate(breaker)