feat: add OCR port family protocols

tests/unit/test_ports.py

@@ -199,3 +199,32 @@ class TestGateUpdate:
             GateUpdate(
                 applied=True, state=GateState.CLOSED, epoch=0, failure_count=-1, retry_after_s=0.0
             )
+
+
+class TestOcrPorts:
+    """M3 三个 OCR Protocol(设计 §3.2): runtime_checkable 结构判定。"""
+
+    def test_ocr_ports_runtime_checkable(self):
+        from polygateway.ports import OcrLayoutPort, OcrTextPort, OcrTransport
+
+        class GoodClient:
+            async def recognize_text(self, image): ...
+            async def parse_layout(self, image): ...
+
+        class GoodTransport:
+            async def recognize_text(self, *, image, source, call_id): ...
+            async def parse_layout(self, *, image, source, call_id): ...
+            async def check_health(self, *, source): ...
+
+        assert isinstance(GoodClient(), OcrTextPort)
+        assert isinstance(GoodClient(), OcrLayoutPort)
+        assert isinstance(GoodTransport(), OcrTransport)
+
+    def test_missing_method_rejected(self):
+        from polygateway.ports import OcrTransport
+
+        class NoHealth:
+            async def recognize_text(self, *, image, source, call_id): ...
+            async def parse_layout(self, *, image, source, call_id): ...
+
+        assert not isinstance(NoHealth(), OcrTransport)