[Copilot]

auto could select an internal utility model that rejects agent custom tools, while detection could stop resolving when small models became unavailable.

• Model eligibility

  • Exclude Copilot utility variants from wildcard matches; preserve explicit pins.
  • Honor picker and policy metadata when present; retain compatibility with ID-only catalogs.
  • Distinguish an exhausted eligible catalog from catalog retrieval failure.

• Detection fallback

  • Expand detection to small → small-agent → agent, preserving the small-model preference.
  • Update documentation and embedded alias maps in generated workflow locks.

• Failure reporting

  • Add regression coverage for the reported custom-tool error, preserving existing non-retryable model_endpoint_mismatch classification.

• Fixes Copilot auto resolves to gpt-5.6-luna-utility, which rejects the agent's custom tools (and detection alias no longer resolves) #72353