This adds a new request type, `SendUserTurn`, that makes it possible to submit a `Op::UserTurn` operation (introduced in #2329) to a conversation. This PR also adds a new integration test that verifies that changing from `AskForApproval::UnlessTrusted` to `AskForApproval::Never` mid-conversation ensures that an elicitation is no longer sent for running `python3 -c print(42)`. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/openai/codex/pull/2345). * __->__ #2345 * #2329 * #2343 * #2340 * #2338