Gateway executor work now inherits the active session contextvars via
copy_context() so background process watchers retain the correct
platform/chat/user/session metadata for routing completion events back
to the originating chat.
Cherry-picked from #10647 by @helix4u with:
- Use asyncio.get_running_loop() instead of deprecated get_event_loop()
- Strip trailing whitespace
- Add *args forwarding test
- Add exception propagation test
8021a735c2