When async_processing=False, the sync path calls execute_command_sync()
which internally uses asyncio.run(). This fails when called from FastAPI's
already-running event loop with 'asyncio.run() cannot be called from a
running event loop'.
Wrapping the call in asyncio.to_thread() runs it in a thread pool executor,
avoiding the event loop conflict while preserving the synchronous behavior
from the API consumer's perspective.
Fixes#453
f14020d385