loopd: read on a socket whose peer closed, instead of failing on macOS

macOS refuses every socket option with EINVAL once the peer has closed
(XNU sosetoptlock, bsd/kern/uipc_socket.c), even with unread data still
buffered. loopd set a read timeout before each read, so on macOS every
frame or response that arrived just before the peer closed was lost:
BrokerPort reported the broker unavailable with "os error 22", and the
llama client failed the same way. Twelve loopd test binaries failed on
macOS; Linux never refuses, so the gate on Talos did not see it.

Both places now go through socket::set_read_timeout, which on Apple
targets takes that one refusal as success: a socket shut in both
directions returns its data or the end at once and cannot block. A
zero timeout is still an error.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/loopd/src/http.rs

@@ -151,9 +151,7 @@ impl Connection {
     }
 
     pub fn set_read_timeout(&self, timeout: Duration) -> Result<(), HttpError> {
-        self.stream
-            .set_read_timeout(Some(timeout))
-            .map_err(HttpError::Io)
+        crate::socket::set_read_timeout(&self.stream, timeout).map_err(HttpError::Io)
     }
 
     pub fn received_any(&self) -> bool {