fix: close makefile wrapper in Python force_stop() to trigger TCP disconnect

Python's socket.makefile() holds its own reference to the socket.
Calling socket.close() alone won't release the OS-level resource
until the makefile wrapper is also closed. This meant force_stop()
wasn't actually closing the TCP connection, so the server never
detected the disconnect and never sent capabilities.changed events
to other clients.

Fix: close the file wrapper before the socket in SocketWrapper.terminate().
Unskip test_capabilities_changed_when_elicitation_provider_disconnects.

Author: MRayermannMSFT

python/copilot/client.py

@@ -2259,6 +2259,13 @@ def __init__(self, sock_file, sock_obj):
                 self._socket = sock_obj
 
             def terminate(self):
+                # Close the file wrapper first — makefile() holds its own
+                # reference to the socket, so socket.close() alone won't
+                # release the OS-level resource until the wrapper is closed too.
+                try:
+                    self.stdin.close()
+                except OSError:
+                    pass
                 try:
                     self._socket.close()
                 except OSError:

python/e2e/test_ui_elicitation_multi_client.py

@@ -225,11 +225,6 @@ async def handler(
 
         await session2.disconnect()
 
-    @pytest.mark.skip(
-        reason="Python force_stop() doesn't trigger server-side capabilities.changed "
-        "reliably in the replay proxy. The equivalent .NET test passes. "
-        "Tracked for follow-up."
-    )
     async def test_capabilities_changed_when_elicitation_provider_disconnects(
         self, mctx: ElicitationMultiClientContext
     ):