Fix guardian review test user input

[jif-oai]

Summary

• Add the missing additional_context field to the guardian review Op::UserInput test initializer.

Test plan

• just fmt
• just test -p codex-core guardian_review
• just test -p codex-core (compiles, then fails on local environment issues: sandbox-exec Operation not permitted, missing test_stdio_server helper binary, and unrelated timeouts)