Fail fast on Copilot SDK model-policy errors and repin Smoke Copilot Sub Agents

[Copilot]

Smoke Copilot Sub Agents was hard-failing on every run before reaching the model: the Copilot SDK returned No model available. Check policy enablement, but the harness did not classify it as a model/policy failure and burned all retries. This change teaches the harness to recognize that error as non-retryable and repins the smoke workflow to a Copilot model that is already serving successfully.

• Error classification

  • Extend Copilot model-unavailable detection to match the SDK policy-enablement error:
    • No model available. Check policy enablement under GitHub Settings > Copilot
  • Route that error through the existing model_not_supported_error path so the workflow reports a clear configuration failure instead of partial_execution.

• Retry behavior

  • Stop retrying deterministic Copilot SDK model/policy failures in the harness.
  • Preserve existing retry behavior for transient partial-execution paths.

• Smoke workflow repin

  • Change the parent model in smoke-copilot-sub-agents from gpt-5.3-codex to gpt-5.4.
  • Regenerate the compiled lock file so the runtime workflow matches the source workflow.

• Regression coverage

  • Add focused tests for:
    • direct detection of the Copilot SDK no-model/policy-enablement error
    • non-retry behavior for that error
    • workflow-output classification via detectCopilotErrors(...)

const MODEL_NOT_SUPPORTED_PATTERN =
  /(?:The requested model is not supported|No model available\.\s*Check policy enablement under GitHub Settings\s*>\s*Copilot)/i;

[github-actions]

Great work on this one — the No model available. Check policy enablement error was a real pain point in the smoke harness, and this PR handles it cleanly end-to-end.

The change is well-scoped: the regex extension in detect_agent_errors.cjs targets exactly the new SDK error string, the non-retry routing in copilot_harness.cjs is surgical, the smoke workflow repin is the logical follow-through, and the regression tests in both .test.cjs files give solid coverage of the new detection path and the non-retry behavior.

This looks ready for review. 🚀

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