feat(perception): add scoped stream control and bounded clock observations

src/k1link/perception/streaming_grpc.py

@@ -149,7 +149,14 @@ class GrpcStreamEndpoint:
             if self.active is not None and self.active[0] == epoch:
                 self.active[1].finish()
 
-    async def serve(self, address: str, *, certificate: bytes, private_key: bytes) -> Any:
+    async def serve(
+        self,
+        address: str,
+        *,
+        certificate: bytes,
+        private_key: bytes,
+        control_handlers: tuple[Any, ...] = (),
+    ) -> Any:
         if not certificate or not private_key:
             raise ValueError("TLS identity is required")
         server = grpc.aio.server(
@@ -158,7 +165,11 @@ class GrpcStreamEndpoint:
                 ("grpc.max_receive_message_length", INPUT_CHUNK),
                 ("grpc.max_send_message_length", MAX_REPLY),
             ),
-            maximum_concurrent_rpcs=2,
+            # aio reserves its next accept before awaiting a request. Leave
+            # one bounded accept slot beside Exchange + a completing Poll;
+            # otherwise the next Poll can inherit a stale "limit exceeded".
+            # Data ownership still admits exactly one Exchange, never 2 GPUs.
+            maximum_concurrent_rpcs=3 if control_handlers else 2,
             compression=grpc.Compression.NoCompression,
         )
         server.add_generic_rpc_handlers(
@@ -166,6 +177,7 @@ class GrpcStreamEndpoint:
                 grpc.method_handlers_generic_handler(
                     SERVICE, {"Exchange": grpc.stream_stream_rpc_method_handler(self.exchange)}
                 ),
+                *control_handlers,
             )
         )
         port = server.add_secure_port(