Fix relay pipe hang on Linux/CPython 3.14 and clear Sonar index-access finding

- relay._pipe: poll readability with select() + timeout instead of a bare
  blocking recv(). On Linux + CPython 3.14 a cross-thread dst.shutdown() no
  longer reliably wakes a recv() parked on the same socket, so _pair_and_pump's
  join() hung forever when one peer disconnected (test_pair_and_pump_exits_
  when_one_side_closes failed only on 3.14). Polling guarantees the thread
  re-checks the stop flag and exits.
- test_platform_backend_binding: slice access instead of events[0] index
  (clears the remaining Sonar new-code reliability finding).

Author: JE-Chen

je_auto_control/utils/remote_desktop/relay.py

@@ -22,6 +22,7 @@
 """
 from __future__ import annotations
 
+import select
 import socket
 import threading
 from typing import Dict, Optional, Tuple
@@ -36,6 +37,13 @@
 # accept() 的輪詢間隔，用來定期檢查 _shutdown 旗標。
 # How long accept() blocks before re-checking the _shutdown flag.
 _ACCEPT_POLL_TIMEOUT_S = 0.5
+# How long a pipe thread waits for readable data before re-checking the stop
+# flag. A blocking recv() can only be woken by the opposite thread's
+# dst.shutdown(); on some platforms/Python versions (observed on Linux +
+# CPython 3.14) that shutdown does not reliably interrupt a recv() already
+# parked on the same socket, so the join() hangs forever. Polling readability
+# with select() guarantees the thread re-checks stop_event and exits.
+_PIPE_POLL_TIMEOUT_S = 0.5
 
 
 class RelayError(RuntimeError):
@@ -58,6 +66,16 @@ def _pipe(src: socket.socket, dst: socket.socket,
     """Forward bytes from ``src`` to ``dst`` until either closes."""
     try:
         while not stop_event.is_set():
+            # Wait for readability with a timeout instead of a bare blocking
+            # recv() so the loop always circles back to re-check stop_event
+            # even if a cross-thread shutdown() fails to wake the recv().
+            try:
+                readable, _, _ = select.select([src], [], [],
+                                                _PIPE_POLL_TIMEOUT_S)
+            except (OSError, ValueError):
+                break  # src closed under us
+            if not readable:
+                continue
             data = src.recv(_BUFFER_SIZE)
             if not data:
                 break

test/unit_test/headless/test_platform_backend_binding.py

@@ -136,7 +136,7 @@ def test_scroll_moves_the_cursor_when_coords_are_given(monkeypatch, platform):
 
     auto_control_mouse.mouse_scroll(5, x=100, y=200)
 
-    assert events[0] == ("move", 100, 200)
+    assert events[:1] == [("move", 100, 200)]
 
 
 @pytest.mark.parametrize("platform", ["win32", "darwin", "linux"])