Restore caller tracing API keys in an environment passed to user code.
Reverts both bootstrap overwrites of the canonical LangSmith key — the
DEEPAGENTS_CODE_-prefixed override and the /auth-stored key — so shell
subprocesses receive the caller's own key rather than the agent's session
key. See original_tracing_api_keys for the rationale; this mirrors
restore_user_tracing_env, which does the same for tracing flags.