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/ocr.py

@@ -44,6 +44,7 @@ from polygateway.types import (
     OcrLayoutResult,
     OcrTextResult,
     Usage,
+    strip_unsupported_extra_body,
 )
 
 if TYPE_CHECKING:
@@ -113,7 +114,9 @@ class OcrClient:
         if quota_full not in ("wait", "fail_fast"):
             raise ValueError(f"quota_full 必须是 wait|fail_fast: {quota_full!r}")
         self._scope = scope
-        self._sources = list(sources)
+        # MonkeyOCR 只发 multipart 表单,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="OCR")
         self._selector = selector
         self._feed_health = isinstance(selector, OutcomeAwareSelector)
         self._quota = QuotaGate(limiter)