feat(trials): freeze failure taxonomy, regrade path, and exit codes

[solomonneas]

Summary

• Freeze the model-trial outcome contract in docs/model-trial-taxonomy.md (Settle the trial failure taxonomy, retry policy, and regrade path before the stable cut #435).
• Add failure_reason on cells (timeout, transport_drop, provider_5xx), drop exit_code from grader_result.v1, and split measurement_failures / partial_scores in summary.json.
• Implement three-valued process exit (0/1/3), brigade model trial regrade, resume regrade for grader_error, and project_cell export privacy.

Closes #435.

Test plan

• brigade work verify run --target . --command "pytest -q tests/ -k 'trial or model_trials or grader or eval'" --capture brigade-work
• ./scripts/verify (3944 passed, 82.49% coverage)
• New tests: regrade without seat rerun, timeout failure_reason, process_exit dominance, project_cell privacy, partial score split

Notes

• --retry-transient intentionally deferred per Settle the trial failure taxonomy, retry policy, and regrade path before the stable cut #435.
• No version bump / release artifacts (contract-only cut).

Made with Cursor

[coderabbitai]

Important

Review skipped

Auto reviews are limited based on label configuration.

🏷️ Required labels (at least one) (1)

• coderabbit-review

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository: escoffier-labs/coderabbit/.coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: a28f8ee4-a2f4-48fb-8881-dba9c34eecfa

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/trial-failure-taxonomy

---

_{Comment @coderabbitai help to get the list of available commands.}