Derive UG_ENABLE_MODEL_DISCOVERY from managed MPS

[andy-xu-db]

Stack

• Derive UG_ENABLE_MODEL_DISCOVERY from managed MPS #694 Shared policy
  • Enable managed model discovery in Claude #701 Claude
    • Cover managed model discovery in Codex #702 Codex

Summary

• Set UG_ENABLE_MODEL_DISCOVERY=1 for the selected agent's managed MPS.
• Set it to 0 otherwise.
• Reject source flags when managed MPS owns routing.
• Scope the variable to the child launch.
• Add no managed-config field.

Reference

• Follows pipe smart routing enabled value down from managed config  #668's per-agent managed-policy and launch-scoped environment pattern.
• Reuses models.model_provider_service.

Test

• 444 focused tests passed.
• Ruff and format checks passed.