Summary

• Fix JS CI failure on main caused by stale security test
• PR feat(interpreter): exec with command argument — execute and don't return #815 changed exec cmd to run within VFS sandbox instead of blocking
• The Rust threat model tests were updated but the JS security test was not
• exec ls now succeeds (exit 0) since ls is a valid builtin in the sandbox
• Changed test to use exec /bin/bash which correctly fails (external binary not in VFS)

Test plan

• All 321 JS tests pass (including updated security test)
• All JS examples pass (bash_basics, data_pipeline, llm_tool, langchain_integration)
• All Rust tests pass (cargo test --all-features)
• cargo fmt --check and cargo clippy clean