[Bug]: bes nowait_for_upload_complete may lead to incomplete uploads when used with plugins

When the CLI uses the BEP backend/proxy events may be lost due to the temporary BEP server quitting along with the CLI process.

Start by tracing the CLI's BEP backend/proxy event flow and the lifetime of the temporary BEP server. Reproduce the plugin upload path and observe whether events are lost when the CLI exits; done means uploads remain complete despite that shutdown.

Written by the indexing model from the issue text.